Spike Lavender

Spike Lavender Seeds (Lavandula latifolia)

Packet of 500 Seeds
Sale price $2.95 Regular price $3.50

Single Packet of 500 Seeds

Product Description

Grow a garden filled with the sweet aroma of Spike Lavender, from freshly harvested Lavandula latifolia seeds. Spike Lavender offers an extremely strong scent, which surpasses other Lavender strains. The plants will mature to a height of roughly 12 to 30 inches tall, producing small, violet colored blooms along it's thin green stems. Spike Lavender doesn't only smell great, it is also very attractive as well. The plants are often seen in many home gardens, as well as parks, zoos and other natural sceneries.

Spike Lavender is categorized as a perennial flowering herb. Perennials such as this will grow quickly from freshly harvested seeds, establishing a deep root system in their initial year of growth. The plants may wilt on the surface, only to return the following year, when all danger of frost has passed. Spike Lavender will make a great addition to your landscaping project, and can be planted along borders, or directly in the garden as well. The plants are known to attract all sorts of beneficial insects to the garden, such as honeybees, bumblebees, butterflies and even hummingbirds. Spike Lavender also makes a great addition to many insectaries and butterfly gardens.

Sowing The Seed

Lavender seeds are best started indoors, 6 to 8 weeks prior to the last killing frost. Start in peat pots, sowing 3 to 5 seeds per pot, at a shallow depth of 1/16” under topsoil. The seeds will require a bit of direct light to properly germinate, so try not to bury them deeper than the recommended depth. Transplant small pots into larger containers if necessary, or transplant directly into the garden, when the weather is warm and all danger of frost has passed.

Growing Conditions

Lavender herbs will require an area of full sunlight for the majority of the day. Temperatures of at least 70F are recommended. A light soil that contains a small amount of gravel will best suit your Lavender plants, as they will need a well draining medium. They are fond of slightly acidic to slightly alkaline soils, with a pH of 6.5 to 8.0. Water the seeds daily with a spray bottle or mist setting, until germination has successfully occurred.

Germination & Growth

Lavender seeds will typically germinate within 7 to 21 days after sowing. Spike Lavender will produce upright plants, which measure anywhere between 12 and 30 inches tall. The plants can be spaced about 12 to 18 inches apart from one another. The violet blooms can be seen through the summer months, and will attract a number of beneficial insects to the garden as well.

Our Promise

We promise to never knowingly carry or sell GMO based seed products. All seeds sold through Seed Needs are Non-GMO products and the vast majority seeds are produced from open pollinated plants. (A very low number of our seed products are F1 hybrids) Our seed stock is stored in a temperature controlled facility and our products are constantly moved out due to popularity. Each and every packet is intended for the current and the following growing season and will not be marked with an expiration date.

If you are to store your seeds for successful growth in the following year, we recommend placing the packets in an airtight ziplock bag. Place your seeds in a cool, dark and dry area of the home, such as a basement where they are kept at room temperature or below.

Our Guarantee

It is our goal to make you a happy customer! If you experience any problems with your seeds such as germination issues, we will replace or refund any seed product within 180 days of your purchase date. Please contact us directly for a resolution to any problems that you are having with our products.

Question: When should I sow these seeds?
Answer: This is something you must research for your specific region. We offer a ton of helpful articles in our Blog that explain in depth how to successfully grow the seeds within our shop. All of our product pages have useful information on sowing as well.

Question: What is the size of this packet?
Answer: Our traditional packages are 3.25" wide, by 4.50" tall. Some of our larger packages of Corn, Beans and Peas will be 4" wide by 4.675" tall, and our Wildflower packages containing bulk seeds are usually 4.50" wide by 6.45" inches tall.

Question: Are your seeds heirloom?
Answer: In short yes, a vast majority of the plant varieties we carry are heirloom. Heirlooms are varieties that have been passed down for generations.

Question: Are your seeds GMO?
Answer: No, we promise to never knowingly carry or supply any GMO based seed products and steer clear of seed producers from major GMO companies, such as Monsanto.

Question: Are your seeds Organic?
Answer: No, at this time we do not sell organic seeds.

Question: How long will shipping take?
Answer: This can sometimes depend on the size of your order, however 95% of our orders will ship within 24 to 48 hours. All orders ship First Class by default and can take 2 - 5 business days to arrive. Orders placed on a Friday may not ship until the following Monday.

Question: What if my seeds don't grow?
Answer: If you experience any problems with our seed products, contact us within 180 days of your purchase date for a resolution.

Question: Do the packages have sowing instructions on them?
Answer: Yes, all of our seed packets have detailed sowing information on the reverse side as well as a QR code that leads to the original product page here on our website.

Question: Why is there no expiration date on your seed packages?
Answer: Our seeds are contained within a temperature controlled facility in airtight containers. When we ship our seed products to customers, we fill a small portion of packets that sell on a weekly basis. We do not print an expiration date on the packets since the large majority of seeds technically do not expire for long periods of time, IF they are stored in the proper conditions. If you plan to store or save your seeds for the following year, we suggest placing them in a ziplock bag, later storing them in a dark, cool and dry area of the home.

Question: Can I receive a catalog in the mail?
Answer: At this time, we are focused on remaining solely online. We do not send paper catalogs in an effort to save more trees, as well as keep our prices low.

Question: I did not receive an invoice for my order.
Answer: We do not send paper invoices with our orders since the invoice can be viewed online with your Seed Needs account. You will also receive an invoice / order confirmation through email.

Question: What is the difference between a hybrid variety and a GMO based seed product.
Answer: Hybrids are a NATURAL process of cross pollinating two species, thus producing a first generation hybrid (F1.) For example: Mixing a red, double blooming, single stem sunflower, with a yellow, multi branching sunflower might result in a orange-red, double blooming, multibranching plant.

GMO based seed products are a completely different and unatural process of gene splicing in a laboratory. The process entails the introduction of a separate biological kingdom, such as a bacteria, or a pesticide. This bacteria or pesticide is then eaten directly by the consumer when the crops reach maturity. (BAD NEWS)

Question: Can you ship these seeds overseas?
Answer: At this time we only ship within the United States and Canada.


Vibration - Wikipedia, the free encyclopedia

Page 1 of 13

From Wikipedia, the free encyclopedia

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road. Vibration is occasionally "desirable". For example the motion of a tuning fork, the reed in a woodwind instrument or harmonica, or the cone of a loudspeaker is desirable vibration, necessary for the correct functioning of the various devices. More often, vibration is undesirable, wasting energy and creating unwanted sound – noise. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven friction, the meshing of gear teeth, etc. Careful designs usually minimize unwanted vibrations. The study of sound and vibration are closely related. Sound, or "pressure waves", are generated by vibrating structures (e.g. vocal cords); these pressure waves can also induce the vibration of structures (e.g. ear drum). Hence, when trying to reduce noise it is often a problem in trying to reduce vibration.

Classical mechanics

Newton's Second Law

History of classical mechanics · Timeline of classical mechanics Branches Statics · Dynamics / Kinetics · Kinematics · Applied mechanics · Celestial mechanics · Continuum mechanics · Statistical mechanics Formulations ■ Newtonian mechanics (Vectorial mechanics) ■ Analytical mechanics:

■ 1 Types of vibration ■ 2 Vibration testing ■ 3 Vibration analysis ■ 3.1 Free vibration without damping ■ 3.1.1 What causes the system to vibrate: from conservation of energy point of view ■ 3.2 Free vibration with damping ■ 3.2.1 Damped and undamped natural frequencies ■ 3.3 Forced vibration with damping ■ 3.3.1 What causes resonance? ■ 3.3.2 Applying "complex" forces to the mass–spring– damper model ■ 3.3.3 Frequency response model ■ 4 Multiple degrees of freedom systems and mode shapes ■ 4.1 Eigenvalue problem ■ 4.2 Illustration of a multiple DOF problem ■ 4.3 Multiple DOF problem converted to a single DOF problem ■ ■ ■ ■ 5 See also 6 References 7 Further reading 8 External links

■ Lagrangian mechanics ■ Hamiltonian mechanics Fundamental concepts Space · Time · Velocity · Speed · Mass · Acceleration · Gravity · Force · Impulse · Torque / Moment / Couple · Momentum · Angular momentum · Inertia · Moment of inertia · Reference frame · Energy · Kinetic energy · Potential energy · Mechanical work · Virtual work · D'Alembert's principle Core topics Rigid body · Rigid body dynamics · Euler's equations (rigid body dynamics) · Motion · Newton's laws of motion · Newton's law of universal gravitation · Equations of motion · Inertial frame of reference · Non-inertial reference frame · Rotating reference frame · Fictitious force · Linear motion · Mechanics of planar particle motion · Displacement (vector) · Relative velocity · Friction · Simple harmonic motion · Harmonic oscillator · Vibration · Damping · Damping ratio · Rotational motion · Circular motion · Uniform circular motion ·

Types of vibration
Free vibration occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at one or more of its "natural frequency" and damp down to zero.

etc.Wikipedia.e. one or more "input" or "control" points located on the DUT-side of a fixture is kept at a specified acceleration. The mass–spring–damper model is an example of a simple harmonic oscillator. Most vibration testing is conducted in a single DUT axis at a time. Generally. but will focus on the major equations and concepts in vibration analysis. The proportionality constant. Non-uniform circular motion · Centripetal force · Centrifugal force · Centrifugal force (rotating reference frame) · Reactive centrifugal force · Coriolis force · Pendulum · Rotational speed · Angular acceleration · Angular velocity · Angular frequency · Angular displacement Scientists Galileo Galilei · Isaac Newton · Jeremiah Horrocks · Leonhard Euler · Jean le Rond d'Alembert · Alexis Clairaut · Joseph Louis Lagrange · Pierre-Simon Laplace · William Rowan Hamilton · Siméon-Denis Poisson Vibration testing Vibration testing is accomplished by introducing a forcing function into a structure. In forced vibration the frequency of the vibration is the frequency of the force or motion applied. even a complex structure such as an automobile body can be modeled as a "summation" of simple mass–spring–damper models. such as road inputs to a moving automobile. usually with some type of shaker. The mathematics used to describe its behavior is identical to other simple harmonic oscillators such as the RLC circuit.[1] Other "response" points experience maximum vibration level (resonance) or minimum vibration level (anti-resonance). free vibration). Please refer to the references at the end of the article for detailed derivations. released in late 2008. springs. a DUT (device under test) is attached to the "table" of a shaker.wikipedia. Examples of this type of vibration include a shaking washing machine due to an 2/3/2011 . Alternately. k.g. Note: In this article the step by step mathematical derivations will not be included. Test Method 527. road. electrodynamic shakers are used. For relatively low frequency forcing. Two typical types of vibration tests performed are random. A random (all frequencies at once) test is generally considered to more closely replicate a real world environment. http://en. The force applied to the mass by the spring is proportional to the amount the spring is stretched "x" (we will assume the spring is already compressed due to the weight of the mass). To start the investigation of the mass–spring–damper we will assume the damping is negligible and that there is no external force applied to the mass (i.). transportation vibration (caused by truck engine. even though most real-world vibration occurs in various axes simultaneously. servohydraulic (electrohydraulic) shakers are used.and sine test. lbf/in or N/m) The force generated by the mass is proportional to the acceleration of the mass as given by Newton’s second law of motion. calls for multiple exciter testing. Vibration analysis The fundamentals of vibration analysis can be understood by studying the simple mass–spring–damper model. Sine (one-frequency-at-a-time) tests are performed to survey the structural response of the device under test (DUT). Indeed. One of the possible modes of vibration of a circular drum (see other modes). For higher frequencies. is the stiffness of the spring and has units of force/distance (e. with order of magnitude being dependent on the actual mechanical system. Free vibration without damping One of the possible modes of vibration of a cantilevered I-beam. the free encyclopedia Page 2 of 13 Forced vibration is when an alternating force or motion is applied to a mechanical system. MIL-STD-810G. or the vibration of a building during an earthquake.Vibration .

This simple relation can be used to understand in general what will happen to a more complex system once we add mass or stiffness. The proportionality constant c is called the damping coefficient and has units of Force over velocity (lbf s/ in or N s/m). the spring tries to return to its un-stretched state (which is the minimum potential energy state) and in the process accelerates the mass. but in a real system there is always something called damping that dissipates the energy and therefore the system eventually bringing it to rest. Simple harmonic motion of the mass –spring system Free vibration with damping We now add a "viscous" damper to the model that outputs a force that is proportional to the velocity of the mass.wikipedia.Vibration . but is normally converted to “standard” frequency (units of Hz or equivalently cycles per second) when stating the frequency of a system. The mass then begins to decelerate because it is now stretching it has been transformed into kinetic energy ( compressing the spring and in the process transferring the kinetic energy back to its potential. Thus oscillation of the spring amounts to the transferring back and forth of the kinetic energy into potential energy. In our simple model the mass will continue to oscillate forever at the same magnitude. the free encyclopedia Page 3 of 13 The sum of the forces on the mass then generates this ordinary differential equation: If we assume that we start the system to vibrate by stretching the spring by the distance of A and letting go. At the point where the spring has reached its un-stretched state all the potential energy that we supplied by ). the above formula explains why when a car or truck is fully loaded the suspension will feel “softer” than unloaded because the mass has increased and therefore reduced the natural frequency of the system. the solution to the above equation that describes the motion of mass is: This solution says that it will oscillate with simple harmonic motion that has an amplitude of A and a frequency of fn.Wikipedia. The number fn is one of the most important quantities in vibration analysis and is called the undamped natural frequency. If you know the mass and stiffness of the system you can determine the frequency at which the system will vibrate once it is set in motion by an initial disturbance using the above stated formula. Every vibrating system has one or more natural frequencies that it will vibrate at once it is disturbed. The damping is called viscous because it models the effects of an object within a fluid. Once we let go of the spring. What causes the system to vibrate: from conservation of energy point of view Vibrational motion could be understood in terms of conservation of energy. For example. In the above example we have extended the spring by a value of x and therefore have stored some potential energy ( ) in the spring. For the simple mass–spring 2/3/2011 . By summing the forces on the mass we get the following ordinary differential equation: http://en. fn is defined as: Note: Angular frequency ω (ω = 2πf) with the units of radians per second is often used in equations because it simplifies the equations.

The cosine function is the oscillating portion of the solution. the quicker it damps to zero. the damped natural frequency is only 1% less than the undamped). over time. A force of this type could. The value that the damping coefficient needs to reach for critical damping in the mass spring damper model is: To characterize the amount of damping in a system a ratio called the damping ratio (also known as damping factor and % critical damping) is used. are determined by the amount the spring is stretched. This damping ratio is just a ratio of the actual damping over the amount of damping required to reach critical damping. engine crankshaft) will have damping factors less than 0.Vibration . for example. and φ. the phase shift. The formulas for these values can be found in the references. but also characterize how a system will behave under forced vibration. This case is called underdamping – this case is of most interest in vibration analysis. be generated by a rotating imbalance.3. What is often done in practice is to experimentally measure the free vibration after an impact (for example by a hammer) and then determine the natural frequency of the system by measuring the rate of oscillation as well as the damping ratio by measuring the rate of decay.1 and 0. The plots to the side present how 0.g.3 damping ratios effect how the system will “ring” down over time. If the damping is small enough the system will still vibrate.wikipedia. The formula for the damping ratio (ζ) of the mass spring damper model is: Mass Spring Damper Model For example. but the frequency of the oscillations is different from the undamped case. http://en. the free encyclopedia Page 4 of 13 The solution to this equation depends on the amount of damping. metal structures (e. but for many practical cases the damping ratio is relatively small and hence the difference is negligible.05 while automotive suspensions in the range of 0.Wikipedia. the initial magnitude. but eventually. Therefore the damped and undamped description are often dropped when stating the natural frequency ( 2/3/2011 . The exponential term defines how quickly the system “damps” down – the larger the damping ratio.1 damping ratio. Forced vibration with damping In this section we will see the behavior of the spring mass damper model when we add a harmonic force in the form below. airplane fuselage. The frequency in this case is called the "damped natural frequency".2–0. The natural frequency and damping ratio are not only important in free vibration. with 0. will stop vibrating. If we increase the damping just to the point where the system no longer oscillates we reach the point of critical damping (if the damping is increased past critical damping the system is called overdamped). The solution to the underdamped system for the mass spring damper model is the following: The value of X. Damped and undamped natural frequencies The major points to note from the solution are the exponential term and the cosine function. fd.g. and is related to the undamped natural frequency by the following formula: The damped natural frequency is less than the undamped natural frequency.

wikipedia. Where “r” is defined as the ratio of the harmonic force frequency over the undamped natural frequency of the mass–spring–damper model. This phenomenon is called resonance (subsequently the natural frequency of a system is often referred to as the resonant frequency). presents one of the most important features in ) the amplitude forced vibration. but with a phase shift φ. of the applied force. The plot of these functions. The phase shift . http://en.Vibration . In rotor bearing systems any rotational speed that excites a resonant frequency is referred to as a critical speed. is defined by the following 2/3/2011 . f. the free encyclopedia Page 5 of 13 If we again sum the forces on the mass we get the following ordinary differential equation: The steady state solution of this problem can be written as: The result states that the mass will oscillate at the same frequency.Wikipedia. In a lightly damped system when the forcing frequency nears the natural frequency ( of the vibration can get extremely high. called "the frequency response of the system". φ. The amplitude of the vibration “X” is defined by the following formula.

the amplitude of the vibration. a square wave). changing the speed of the machine generating the force).5 second. If no damping exists. the more the motion. is reduced in this region. if you double the force. the free encyclopedia Page 6 of 13 If resonance occurs in a mechanical system it can be very harmful – leading to eventual failure of the system. This type of force has the shape of a 1 Hz square wave. X. you need to push at the correct moment if you want the swing to get higher and higher. What causes resonance? Resonance is simple to understand if you view the spring and mass as energy storage elements – with the mass storing kinetic energy and the spring storing potential energy. Hence. In the case of our square wave force. Since the deflection seen in the spring. ■ At a given frequency ratio. perhaps the forcing frequency can be shifted (for example.Vibration . let us apply a force to the mass–spring–damper model that repeats the following cycle – a force equal to 1 newton for 0. ■ When r ≫ 1 the amplitude of the vibration is actually less than the static deflection δst. more damping actually reduces the effects of vibration isolation when r ≫ 1 because the damping force (F = cv) is also transmitted to the base. the vibration doubles) ■ With little or no damping. If the system cannot be changed. Therefore a point will come when the energy dissipated by the damper will equal the energy being fed in by the force. the force applied does not necessarily have to be high to get large motions. impulses) and random functions.5 second and then no force for 0. the more the damper dissipates the energy. Applying "complex" forces to the mass–spring–damper model In a previous section only a simple harmonic force was applied to the model. http://en. As in the case of the swing. when the mass and spring have no force acting on them they transfer energy back and forth at a rate equal to the natural frequency. With the advent of the modern computer the Fourier transform is almost always computed using the Fast Fourier Transform (FFT) computer algorithm in combination with a window function.5 newton and is represented by a value at "0" Hz in the frequency spectrum. This is shown by the line at 1 Hz. In this region the force generated by the mass (F = ma) is dominating because the acceleration seen by the mass increases with the frequency. is directly proportional to the amplitude of the force F0 (e. The next component is a 1 Hz sine wave with an amplitude of 0. the force transmitted by the spring (F = kx) to the base is reduced. the first component is actually a constant force of 0. adding damping can significantly reduce the magnitude of the vibration. Therefore the mass–spring–damper system is isolating the harmonic force from the mounting base – referred to as vibration isolation. The Fourier transform of the square wave generates a frequency spectrum that presents the magnitude of the harmonics that make up the square wave (the phase is also generated. dissipates energy. For example. but this can be extended considerably using two powerful mathematical tools. instead of storing energy. As the amplitude plot shows. Hence. The damper. but is typically of less concern and therefore is often not plotted). Since the damping force is proportional to the 2/3/2011 . the Fourier transform allows you to interpret the force as a sum of sinusoidal forces being applied instead of a more "complex" force (e. the vibration is in phase with the forcing frequency when the frequency ratio r < 1 and 180 degrees out of phase when the frequency ratio r > 1 ■ When r ≪ 1 the amplitude is just the deflection of the spring under the static force F0. Applying a force to the mass and spring is similar to pushing a child on swing.g. Also. Consequently. As discussed earlier. one of the major reasons for vibration analysis is to predict when this type of resonance may occur and then to determine what steps to take to prevent it from occurring.g. The following are some other points in regards to the forced vibration shown in the frequency response plots. Interestingly.wikipedia. The first is the Fourier transform that takes a signal as a function of time (time domain) and breaks it down into its harmonic components as a function of frequency (frequency domain).Wikipedia. The remaining components are at odd frequencies and it takes an infinite amount of sine waves to generate the perfect square wave.g. when r ≪ 1 the effects of the damper and the mass are minimal. the pushes just need to keep adding energy into the system. This deflection is called the static deflection δst. the magnitude can be reduced if the natural frequency can be shifted away from the forcing frequency by changing the stiffness or mass of the system. there is nothing to dissipate the energy and therefore theoretically the motion will continue to grow on into infinity. X. the system has reached its maximum amplitude and will continue to vibrate at this level as long as the force applied stays the same.64. At this point. if energy is to be efficiently pumped into both the mass and spring the energy source needs to feed the energy in at a rate equal to the natural frequency. In other words. The Fourier transform can also be used to analyze non-periodic functions such as transients (e.

http://en. spring stiffness of 1. where The phase of the FRF was also presented earlier as: For example. but not technically as accurate) and has both a magnitude and phase component (if represented as a complex number. "the principle of superposition".wikipedia. The frequency response of the mass–spring–damper therefore outputs a high 7 Hz vibration even though the input force had a relatively low 7 Hz harmonic. the system is linear if the spring force is proportional to the displacement and the damping is proportional to the velocity over the range of motion of interest. Frequency response model We can view the solution of a vibration problem as an input/output relation – where the force is the input and the output is the vibration.Vibration . The magnitude of the frequency response function (FRF) was presented earlier for the mass–spring–damper system. The values of the spring and mass give a natural frequency of 7 Hz for this specific system. The second mathematical tool.Wikipedia. but the Fourier transform will in general give multiple harmonic forces. allows you to sum the solutions from multiple forces if the system is linear. This is done by performing an inverse Fourier Transform that converts frequency domain data to time domain. In practice.1. The figure also shows the time domain representation of the resulting vibration. The figure illustrates the resulting vibration. let us calculate the FRF for a mass–spring–damper system with a mass of 1 kg. If we apply the 1 Hz square wave from earlier we can calculate the predicted vibration of the mass. Click and go to full resolution for an animation H(ω) is called the frequency response function (also referred to as the transfer function. this is rarely done because the frequency spectrum provides all the necessary information. In the case of the spring–mass–damper model. It happens in this example that the fourth harmonic of the square wave falls at 7 2/3/2011 .93 N/mm and a damping ratio of 0. a real and imaginary component). the free encyclopedia Page 7 of 13 In the previous section. the solution to the problem with a square wave is summing the predicted vibration from each one of the harmonic forces found in the frequency spectrum of the square wave. This example highlights that the resulting vibration is dependent on both the forcing function and the system that the force is applied to. the vibration solution was given for a single harmonic force. If we represent the force and vibration in the frequency domain (magnitude and phase) we can write the following relation: How a 1 Hz square wave can be represented as a summation of sine waves(harmonics) and the corresponding frequency spectrum. Hence.

The equations of motion of the 2DOF system are found to be: 2 degree of freedom model We can rewrite this in matrix format: A more compact form of this matrix equation can be written as: http://en. damping. In the case of more complex systems we need to discretize the system into more masses and allow them to move in more than one direction – adding degrees of freedom. Multiple degrees of freedom systems and mode shapes The simple mass–spring damper model is the foundation of vibration analysis. if you apply a known force and sweep the frequency and then measure the resulting vibration you can calculate the frequency response function and then characterize the system. The major concepts of multiple degrees of freedom (MDOF) can be understood by looking at just a 2 degree of freedom model as shown in the figure.Wikipedia. the free encyclopedia Page 8 of 13 Frequency response model The frequency response function (FRF) does not necessarily have to be calculated from the knowledge of the mass. This technique is used in the field of experimental modal analysis to determine the vibration characteristics of a structure. For example. but what about more complex systems? The mass–spring–damper model described above is called a single degree of freedom (SDOF) model since we have assumed the mass only moves up and 2/3/2011 .Vibration . and stiffness of the system.wikipedia. but can be measured experimentally.

Eigenvalue problem This is referred to an eigenvalue problem in mathematics and can be put in the standard format by pre-multiplying the equation by and if we let and The solution to the problem results in N eigenvalues (i. The eigenvalues provide the natural frequencies of the system.wikipedia.e.Vibration . and stiffness matrices. The solution of an eigenvalue problem can be quite cumbersome (especially for problems with many degrees of freedom). the values of that correspond to each eigenvalue are called the 2/3/2011 . The exponential solution is only used because it easier to manipulate mathematically. The equation then becomes: Since e iωt cannot equal zero the equation reduces to the following. damping. The matrices are NxN square matrices where N is the number of degrees of freedom of the system. The eigenvalues and eigenvectors are often written in the following matrix format and describe the modal model of the system: and http://en. the free encyclopedia Page 9 of 13 where and are symmetric matrices referred respectively as the mass.[2] This differential equation can be solved by assuming the following type of solution: Note: Using the exponential solution of is a mathematical trick used to solve linear differential equations. In the following analysis we will consider the case where there is no damping and no applied forces (i. ). When these eigenvalues are substituted back into the original set of equations. where N corresponds to the number of degrees of freedom.e.Wikipedia. If we use Euler's formula and take only the real part of the solution it is the same cosine solution for the 1 DOF system. free vibration). The solution of a viscously damped system is somewhat more complicated. but fortunately most math analysis programs have eigenvalue routines. These eigenvectors represent the mode shapes of the system. 2/3/2011 . In this case. The mode shape vectors are not the absolute motion. the best method of visualizing the mode shapes is by animating them. but just describe relative motion of the degrees of freedom. Since the system is a 2 DOF system. Even this relatively simple model has over 100 degrees of freedom and hence as many natural frequencies and mode shapes.Vibration . a finite element model was used to generate the mass and stiffness matrices and solve the eigenvalue problem.Wikipedia. there are two modes with their respective natural frequencies and shapes. In general only the first few modes are important. The mass and stiffness matrix for this problem are then: and Then The eigenvalues for this problem given by an eigenvalue routine will be: The natural frequencies in the units of hertz are then (remembering The two mode shapes for the respective natural frequencies are given as: ) and . each mass is moving in opposite direction at the same rate. Let both masses have a mass of 1 kg and the stiffness of all three springs equal 1000 N/m. the free encyclopedia Page 10 of 13 A simple example using our 2 DOF model can help illustrate the concepts. In our case the first mode shape vector is saying that the masses are moving together in phase since they have the same value and sign. An example of animated mode shapes is shown in the figure below for a cantilevered I-beam. In the case of the second mode shape vector. Illustration of a multiple DOF problem When there are many degrees of freedom. http://en.

the orthogonality properties are often used to scale the eigenvectors so the modal mass value for each mode is equal to 1. If we use this coordinate transformation in our original free vibration differential equation we get the following equation.Wikipedia. (Note: Since the eigenvectors (mode shapes) can be arbitrarily scaled. It can be shown that the eigenvectors have the following properties: and are diagonal matrices that contain the modal mass and stiffness values for each one of the modes.wikipedia. We can take advantage of the orthogonality properties by premultiplying this equation by The orthogonality properties then simplify this equation to: http://en.Vibration . the free encyclopedia Page 11 of 13 The mode shapes of a cantilevered I-beam 1st lateral bending 1st torsional 1st vertical ben 2nd lateral bending 2nd torsional 2nd vertical ben Multiple DOF problem converted to a single DOF problem The eigenvectors have very important properties called orthogonality properties. These properties can be used to greatly simplify the solution of multi-degree of freedom 2/3/2011 . The modal mass matrix is therefore an identity matrix) These properties can be used to greatly simplify the solution of multi-degree of freedom models by making the following coordinate transformation.

ISBN 0-195-142462 Inman.[2] The key is that the modal and stiffness matrices are diagonal matrices and therefore we have "decoupled" the equations. EE-Evaluation Engineering. and Harshness Quantum vibration Random vibration Ride quality Shock Simple harmonic oscillator Sound Structural acoustics Structural dynamics Tire balance Torsional vibration Vibration control Vibration isolation Vibration of rotating structures Wave Whole body vibration References 1. Engineering Vibration. 2001.. 2/3/2011 . the free encyclopedia Page 12 of 13 This equation is the foundation of vibration analysis for multiple degree of freedom systems. Benson. Instead of solving for x we are instead solving for q. It may be clearer to understand if we write as: Written in this form we can see that the vibration at each of the degrees of freedom is just a linear sum of the mode shapes. ISBN 0-201-50156-2 Thompson. See also ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Balancing machine Base isolation Cushioning Critical speed Damping Dunkerley's Method Earthquake engineering Fast Fourier transform Journal of Sound and Vibration Mechanical resonance Modal analysis Mode shape Noise and vibration on maritime vessels Noise. Silva. Singiresu. Prentice Hall. 1990. In other words. ISBN 013726142X Rao. Theory of . Vibration. Theoretical And Experimental Modal Analysis. Wayne. A similar type of result can be derived for damped systems. Nelson Thornes Ltd. Principles of Vibration.Wikipedia. Daniel J. 2006 2. Mechanical Vibrations. Research Studies Press Ltd. 2001. ^ Tustin.Vibration . we have transformed our problem from a large unwieldy multiple degree of freedom problem into many single degree of freedom problems that can be solved using the same methods outlined above. 1997. how much each mode "participates" in the final vibration is defined by q. 1996. referred to as the modal coordinates or modal participation factors.T.wikipedia. its modal participation factor. ^ a b Maia. Where to place the control accelerometer: one of the most critical decisions in developing random vibration tests also is the most neglected (http://findarticles.. ISBN 0-412-783908 http://en. Addison Wesley. Oxford University Pres. ISBN 0471970670 Further reading ■ ■ ■ ■ Tongue. Furthermore.

Dover ■ Structural Dynamics and Vibration Laboratory of McGill University (http://structdynviblab.mat. a non-profit ■ Normal vibration modes of a circular membrane (http://web. http://en. See Terms of Use for details. Mechanical Vibrations.wikipedia.Wikipedia. Wikipedia® is a registered trademark of the Wikimedia Inc. ■ Text is available under the Creative Commons Attribution-ShareAlike License.phyastr.bham.Vibration . Oscillation/Vibration Concepts (http://hyperphysics. the free encyclopedia Page 13 of 13 ■ Hartog.html) Retrieved from "" Categories: Mechanical vibrations | Mechanical engineering ■ This page was last modified on 19 January 2011 at 08:37. ISBN 0-486-647854 External links ■ Hyperphysics Educational Website. 1985. Den.J.html#permot) ■ Nelson Publishing.wikipedia. Evaluation Engineering Magazine ( 2/3/2011 . additional terms may apply.

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New bird species with musical tone discovered in India

New bird species with musical tone discovered in India

New Delhi: A team of international scientists has discovered a new species of bird with a soothing tone in northeastern India and adjacent parts of China.

The scientific name honours the great Indian ornithologist Salim Ali, in recognition of his contributions to the development of Indian ornithology and nature conservation.

The discovery process for the Himalayan forest thrush began in 2009 when it was realised that what was considered a single species, the plain-backed thrush Zoothera mollissima, was in fact two different species in northeastern India, said Pamela Rasmussen from Michigan State University in the US.

Shashank Dalvi from Bengaluru-based National Centre of Biological Sciences was also part of the research team.

What first caught scientists’ attention was the plain-backed thrush in the coniferous and mixed forest had a rather musical song, whereas those found in the same area – on bare rocky ground above the treeline – had a much harsher, scratchier, unmusical song.

“It was an exciting moment when the penny dropped, and we realised that the two different song types from plain-backed thrushes that we first heard in northeast India in 2009, and which were associated with different habitats at different elevations, were given by two different species,” said lead researcher Per Alstrom of Uppsala University in Sweden.

Along with keen field observations, the scientists had to do a lot of sleuthing with museum specimens.

Investigations involving collections in several countries revealed consistent differences in plumage and structure between birds that could be assigned to either of these two species.

It was confirmed that the species breeding in the forests of the eastern Himalayas had no name.

Further analyses of plumage, structure, song, DNA and ecology from throughout the range of the plain-backed thrush revealed that a third species was present in central China.

This was already known but was treated as a subspecies of plain-backed thrush. The scientists called it Sichuan forest thrush.

The song of the Sichuan forest thrush was found to be even more musical than the song of the Himalayan forest thrush.


hillary clinton

Clinton Now Blaming Sanders for “Lasting Damage” After Electoral Evisceration

Chances are, if you are a part of the democratic party, Hillary Clinton will end up blaming you for one of her multitude of failures before she leaves politics.

The former First Lady was an abysmal choice for the democrats in 2016, given her immense and inescapable closet full of skeletons.  Clinton herself was already the punchline to many a joke in Washington and beyond thanks to her reputation as a hawkish, corrupt brute who refused to be stopped by a lack of public trust in her capabilities.

Furthermore, in 2016’s contest, Clinton was found to be flawed in ways that transcended her politics.  The former Secretary of State was often seen being assisted with stairs, having seizure-like moments, and collapsing on a breezy day in New York City just a year ago.  In other words, the American people had no confidence in her physical capability to lead, let alone her scandalous past.

Then came the leaks.

Clinton’s camp had been targeted by an insider, looking to expose the flawed candidate for exactly what she was:  A conniving and corrupt career criminal who would stop at absolutely nothing to fulfill her quest for ultimate power.  In the leaks, that were likely sent to Wikileaks by later-murderd DNC staffer Seth Rich, Clinton’s campaign was shown to be colluding with the DNC in order to stifle the efforts of challenger Bernie Sanders, as well as procuring an inside track to the mainstream media, gaining access to debate questions long before the events began.

Now, however, Clinton is slithering around the nation attempting to rewrite the record of her historically embarrassing loss.  In her latest book, the defeated democrat blames nearly everyone for her failure in 2016, not the least of which was her primary opponent Bernie Sanders.

“Hillary Clinton casts Bernie Sanders as an unrealistic over-promiser in her new book, according to excerpts posted by a group of Clinton supporters.

“She said that his attacks against her during the primary caused ‘lasting damage’ and paved the way for ‘(Donald) Trump’s “Crooked Hillary” campaign.’
“Clinton, in a book that will be released September 12 entitled ‘What Happened,’ said Sanders ‘had to resort to innuendo and impugning my character’ because the two Democrats ‘agreed on so much.’
“‘When I finally challenged Bernie during a debate to name a single time I changed a position or a vote because of a financial contribution, he couldn’t come up with anything,’ Clinton wrote.
“‘Nonetheless, his attacks caused lasting damage, making it harder to unify progressives in the general election and paving the way for Trump’s “Crooked Hillary” campaign.'”
Of course, these assertions by the incorrigible Clinton are not finding a roost within the currently imploding democratic party.
The democrats themselves rejected Clinton wholeheartedly during the primaries, forcing Clinton to resort to bribery, blackmail, and a number of other similarly salacious actions in order to coerce the DNC to nominate her for President.  Meanwhile, the bulk of the party was turning to Sanders as the non-establishment candidate best suited for going toe to toe with Donald Trump in the general election.

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Hamsters are cute little pets who don’t require a lot of care. Watching a hamster stuff food into its cheek pouches is a lot of fun, as well as seeing a hamster climb through a series of tubes and run on its exercise wheel.

There are two types of hamsters commonly sold as pets, the better known species called the Syrian hamster, about 6-8" long, and the dwarf hamsters, never larger than 4" long. The Syrian hamster comes in many different colors and coat types, including the long haired teddy bear hamster.

Young hamsters can be shy and need to be tamed, so they make good pets for adults and older children.

One hamster, or more?

Syrian hamsters are solitary animals and can only be kept one to a cage. Dwarf hamsters are more social, and can live in groups as long as they are introduced when young, and the cage is large enough.

The basic hamster diet should be a fortified grain mix along with commercial rodent blocks. You can also give hamsters small amounts of veggies and other healthy foods. Treats are great for training and strengthening the bond between you and your hamsters and can comprise 10% of their diet.

A hamster cage can be made of wire, plastic, or glass. It is probably best to choose a combination of wire and plastic for the best ventilation. Some hamsters have a tendency to chew on plastic, and all hamsters have a tendency to try to escape their cage, so make sure it is secure. For bedding you can choose from aspen shavings or pet litter of recycled paper or organic pellets. Do not use clay litter or cedar shavings. Some hamsters will use a special hamster litter box.

Hamsters need a water bottle and a small food a dish. For their bed choose from plastic, wood, or grass houses and/or a hammock or sleeping bag. They need an exercise wheel, and also enjoy tubes, climbing toys such as ladders, ropes, and branches, and chew toys.

Clean the cage and accessories weekly. Be sure to remove all stored food and scrub all parts of the water bottle and replace the bottle every six months.

Health care

With proper care and diet, hamsters tend to be healthy animals. Bad smelling diarrhea or wetness under the tail are usually signs of a serious problem.

Special needs

Hamsters need more time than most small pets to socialize to people. Syrian hamsters are very nocturnal and do not like to be disturbed during the day. Very cold temperatures can cause a hamster to hibernate, which can cause it to appear dead.

Life cycle

Syrian hamsters live an average of 2-3 years, although it’s possible for them to live 5 years. Hamsters can breed as early as 3 weeks of age but should not until 4 months. The gestation period is 16 days and the average litter size is 6-8. Baby hamsters open their eyes at 18 days and can be weaned at 4 weeks.

Dwarf hamsters live an average of 2 years, although it’s possible for them to live 3 years. They can breed as early as 4-5 weeks of age but should not until 3 months. The gestation period is 18-21 days and the average litter size is 5-6. The babies open their eyes at 12 days and can be weaned at 4-5 weeks.

Expert Help

If you have questions about your hamster, do not hesitate to contact us. We will be happy to help you choose a hamster care book for more complete information.

Supplies Checklist:

Bedding and/or litter

Water bottle

Moist Food dish

Hamster food

Litter box (optional)

Exercise wheel

Activity toys

Chew toys


Daradi is a minor character in Horizon Zero Dawn. She is a young Carja noble whom the Nora Brave Aloy met at the former's family estate.

When the estate was attacked by machines, her father locked her in a room to protect her, before being subsequently killed by the machines.

She was found and released by Aloy, who was investigating the machine attacks on the estate. Before releasing her, Aloy had found and destroyed a Machine Lure on the grounds which was attracting them. When Aloy told her that her brother Ranaman asked her to do this, she informed Aloy that Ranaman had been disowned and cast out of the family by their father for being a greedy, murderous criminal. This made Aloy realize that Ranaman had planted the lure to kill Daradi, their father, and everyone else on the estate to claim it as the sole heir.

Ranaman appeared with another lure and smugly promised death to her and Aloy by the machines. However, one of those same machines killed him, destroying the new lure in the process. Daradi again took refuge in the house while Aloy successfully killed the machines. In gratitude, she gave Aloy a Remarkable Reward Box.

Associated Quests

Carja Characters
Sun-Court Avad - Cantarah - Irid - Itamen - Jahamin - Marad - Namman - Nasadi
Carja Guard Balahn - Firiv - Janeva - Lakhir - Walid - Zaid
Carja Tribe Members Daradi - Dirid - Elida - Enasha - Gavan - Gulahni - Hashiv - Three-Toe Huadiv - Ilsadi - Keadi - Kindiv - Kudiv - Lahavis - Lubavad - Marzavid - Nasan - Nil (formerly) - Omas - Studious Palas - Quarry Foreman - Ranaman - Smiling Ranin - Ravan - Ravan's Steward - Rokasha - Shahavad - Uthid - Vanasha - Vashad
Hunters Lodge Ahsis - Aidaba - Bashad - Greatrun Keeper - Havash - Ligan - Malesh - Palaved - Spurflints Keeper - Sun Furrows Keeper - Talanah - Tufanah - Valleymeet Keeper

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2017 IAG Conference FAQ

Q: When does registration open?
A: Tuesday, September 5th

Q. What is the cost?
A: Member Cost: $305 for Full Conference / $210 for one day only (Mon or Tues)
New-Member Cost: $340 for Full Conference / $240 for one day only (Mon or Tues)
*All registrations permit entry to Parent Night on Sunday from 6:00-7:00

Q. Where is the conference?
A: The conference will take place at the Indianapolis Downtown Marriott located at 350 W. Maryland St, Indianapolis, IN 46225.

Q: Is there a special rate on hotel rooms?
A: Yes! Go to this link to book your room at the IAG rate

Q: What are ticketed sessions?

A: The first session of each day is a ticketed session. Registrants need to choose which session they would like to attend. This ensures the registrant a seat in this featured session. All other sessions during the day are breakout sessions, which are first come, first serve for seating. We will also have a keynote presentation each day following lunch.

Q: What are the payment options?
A: You may pay by credit card via Paypal or by purchase order. Registrants paying by PO must enter the purchase order number. Schools may have multiple registrants on the same order; simply use the same PO number.

Q: How do I know if I am a member?
A: You receive messages directly from IAG (not forwards). You attended the conference last year as an individual (not under an institutional membership).
If you are not sure, just write Jason at iagwebmaster@mac.com; he will help you.

Q: Is IAG membership still complementary with registration?
A: Yes! Individuals will receive a 1 year IAG membership. Also, our institutional membership holders will receive a 1 year extension if they register 5 people for the conference.

Q: What time does conference start and end each day?
8:00-4:05 PM on Monday
8:00-2:55 PM on Tuesday

Q: Are lunch and breakfast included?
A: Yes! Breakfast and coffee will be out in the morning during check-in and lunch is served before the keynote presentation each day.

Q: Is parking included?
A: No, please plan accordingly.

Q: Should I register as soon as possible?
A: Yes! We have limited space available. On the registration form, you will be able to see how many seats are still available for each session. Registration opens on September 5th, 2017.

Q: Can I register more than one person on a form?
A: No. Each registrant needs to complete a form to register.


Month: August 2016

Change IS Good

Despite what many people think, change is actually a good thing.

Our world has changed over centuries, has continued to do it to this day, and will continue to do it until the end of time. In essence, shouldn’t that mean that if change is constant then shouldn’t we adapt to changing with it?

If you aren’t growing then you’re dying inside. And if you aren’t growing then you simply aren’t open to changing. In an amazing book I finished today I adopted a quote that will forever stick in my brain that reads: “If you do not change, you can become extinct.” Therefore, without change one cannot continue to grow.

If you let the fear of change or refusal to acknowledge it continuously interrupt the natural process of change in your life, then you will always stay in the same place. You will always get the same results by always applying the same actions. Kind of a scary thought isn’t it? To grow old and be regretful of the many things you let fear stop you from doing could be devastating.

Typically, the fear of change is always much larger than it should be due the irrational appearance your mind creates of it when you repeatedly revisit the concept of it. No matter how scary something is, the actual truth is that things are never scarier than we imagine them to be and fear is created from just that-your imagination. The thought of what would happen if we don’t take on these fears is much scarier than the process of overcoming the actual fear itself.  Continue reading “Change IS Good”

Motivation For Success From Steve Jobs That Can Change Your Life

We can all learn a lesson about success from the late Steve Jobs. The things he did with Apple and Pixar revolutionized the world as we know it and without these wonderful creations, things would certainly not be the same.

These were massive successes that required a lot of hard work and a hulk like mentality, and overcoming other adversities that almost no other person would be willing to face. This is the exact point I wanted to make here today.

The old saying may be cliche and like a fairy tale myth to most people-“Whatever you can believe you can achieve.” Steve Jobs is a shining example of this.

Most people are so comfortable with what they have and uninspired to reach unfound levels of success in their lives that even the thought of a little hard work hurts their head or ego. Then then go on to complain about the things they don’t have and never will because they’re too unlikely to strike it rich.

This kind of mentality will kill your dreams and goals from the start, leaving you to fester in your own sea of negativity and limiting beliefs.

The commencement speech in the video below is information that every student should have a chance to hear. These are life-changing words that if more people heard then maybe our economy wouldn’t be as devastating as it is today. More people would be more inspired to recognize their dreams and turn them into a reality.

Continue reading “Motivation For Success From Steve Jobs That Can Change Your Life”

Most Things, If Not Everything, Happens for a Reason

Some of you may think this will sound like a bunch of hocus pocus or witchery but one of the most important things I have learned in my life is that everything happens for a reason.

Whether you believe in God, law of attraction, etc, have you considered that one or all of these could be responsible for the events that transpire in your life? Some people believe God has a plan for them while others believe that you attract what you put out into the Universe. I believe in both.

I used to be a very negative person with a pessimistic outlook on life. I complained often and had taken on the role of a victim. I wondered why everything bad happened to me and what I had done to deserve bad things happening to me.

I had no idea I was like this at the time and didn’t realize it until years later after I had severely worked on my personal growth and development. I read many books and listened to positive audios on a daily basis. I began to learn every day, which resulted in more positive thoughts, and my brain functioning at a higher frequency. I began to see the good in every situation which gave me peace of mind and allowed me to enter a new plane of spirituality.  Continue reading “Most Things, If Not Everything, Happens for a Reason”


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ACOUSTICS part – 3 Sound Engineering Course

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Presentation on theme: "ACOUSTICS part – 3 Sound Engineering Course"— Presentation transcript:

1 ACOUSTICS part – 3 Sound Engineering Course
Angelo Farina Dip. di Ingegneria Industriale - Università di Parma Parco Area delle Scienze 181/A, Parma – Italy

2 The Sound Intensity meter

3 Euler equation: the sound intensity probe
A sound intensity probe is built with two amplitude and phase matched pressure microphones: The particle velocity signal is obtained integrating the difference between the two signals:

4 Euler’s Equation Connection between sound pressure and particle velocity; it is derived from the classic Newton’s first law ( F = m · a ): It allows to calulate particle velocity by time-integrating the pressure gradient: The gradient is (approximately) known from the difference of pressure sampled by means of two microphones spaced a few millimeters (SOund Intensity probe).

5 Sound Intensity probe (1)
The Sound Intensity is: Where both p and v can be derived by the two pressure signals captured by the two microphones

6 Sound Intensity probe (2)

7 Sound Intensity Probe: errors
Phase Mismatch Error due to a phase error of 0.3° in a plane propagating wave Finite-Differences Error of a sound intensity probe with 1/2 inch microphones in the face-to-face configuration in a plane wave of axial incidence for different spacer lengths: 5 mm (solid line); 8.5 mm (dashed line); 12 mm (dotted line); 20 mm (long dashes); 50 mm (dash-dotted line)

8 Microphones

9 Omnidirectional microphones
ISO3382 recommends the usage of omni mikes of no more than 13mm These are the same microphones usually employed on sound level meters: Sound Level Meter (records a WAV file on the internal SD) (left) Measurement-grade microphone and preamplifier (to be connected to a sound card)(right)

10 Spatial analysis by directive microphones
The initial approach was to use directive microphones for gathering some information about the spatial properties of the sound field “as perceived by the listener” Two apparently different approaches emerged: binaural dummy heads and pressure-velocity microphones: Binaural microphone (left) and variable-directivity microphone (right)

11 Test with binaural microphones
Cheap electret mikes in the ear ducts

12 Capturing Ambisonics signals
A tetrahedrical microphone probe was developed by Gerzon and Craven, originating the Soundfield microphone

13 Soundfield microphones

14 Soundfield microphones
The Soundfield microphone allows for simultaneous measurements of the omnidirectional pressure and of the three cartesian components of particle velocity (figure-of-8 patterns)

15 Directivity of transducers
Soundfield ST-250 microphone

16 Alternative A-format microphones
Nuove tecnologie Innovazioni Tecnologiche Audio 06/03/2009 01/03/2010 Alternative A-format microphones At UNIPR many other 1st-order Ambisonics microphones are employed (Soundfield TM, DPA-4, Tetramic, Brahma) 16 Leonardo Scopece Leonardo Scopece 16 16

17 Portable, 4-channels microphone
A portable digital recorder equipped with tetrahedrical microphone probe: BRAHMA

18 Outdoors propagation

19 The D’Alambert equation
The equation comes from the combination of the continuty equation for fluid motion and of the 1st Newton equation (f=m·a). In practive we get the Euler’s equation: now we define the potential F of the acoustic field, which is the “common basis” of sound pressure p and particle velocity v: Subsituting it in Euler’s equation we get:: D’Alambert equation Once the equation is solved and F is known, one can compute p and v.

20 Free field propagation: the spherical wave
Let’s consider the sound field being radiated by a pulsating sphere of radius R: v(R) = vmax ei ei = cos() + i sin() Solving D’Alambert equation for r > R, we get: Finally, thanks to Euler’s formula, we get back pressure: k = w/c wave number

21 Free field: proximity effect
From previous formulas, we see that in the far field (r>>l) we have: But this is not true anymore coming close to the source. When r approaches 0 (or r is smaller than l), p and v tend to: This means that close to the source the particle velocity becomes much larger than the sound pressure.

22 Free field: proximity effect
The more a microphone is directive (cardioid, hypercardioid) the more it will be sensitive to the partcile velocty (whilst an omnidirectional microphone only senses the sound pressure). So, at low frequency, where it is easy to place the microphone “close” to the source (with reference to l), the signal will be boosted. The singer “eating” the microphone is not just “posing” for the video, he is boosting the low end of the spectrum...

23 Free field: Impedance If we compute the impedance of the spherical field (z=p/v) we get: When r is large, this becomes the same impedance as the plane wave (r ·c). Instead, close to the source (r < l), the impedance modulus tends to zero, and pressure and velocity go to quadrature (90° phase shift). Of consequence, it becomes difficult for a sphere smaller than the wavelength l to radiate a significant amount of energy.

24 Free Field: Impedance

25 Free field: energetic analysis, geometrical divergence
The area over which the power is dispersed increases with the square of the distance.

26 Free field: sound intensity
If the source radiates a known power W, we get: Hence, going to dB scale:

27 Free field: propagation law
A spherical wave is propagating in free field conditions if there are no obstacles or surfacecs causing reflections. Free field conditions can be obtained in a lab, inside an anechoic chamber. For a point source at the distance r, the free field law is:  Lp = LI = LW - 20 log r log Q (dB)   where LW the power level of the source and Q is the directivity factor. When the distance r is doubled, the value of Lp decreases by 6 dB.

28 Free field: directivity (1)
Many soudn sources radiate with different intensity on different directions. Hence we define a direction-dependent “directivity factor” Q as: Q = I / I0 where I è is sound intensity in direction , and I0 is the average sound intensity consedering to average over the whole sphere. From Q we can derive the direcivity index DI, given by: DI = 10 log Q (dB) Q usually depends on frequency, and often increases dramatically with it. Iq I0

29 Free Field: directivity (2)
Q = 1  Omnidirectional point source Q = 2  Point source over a reflecting plane Q = 4  Point source in a corner Q = 8  Point source in a vertex

30 Outdoor propagation – cylindrical field

31 Geometry for propagation from a line source to a receiver
Line Sources Many noise sources found outdoors can be considered line sources: roads, railways, airtracks, etc. Geometry for propagation from a line source to a receiver in this case the total power is dispersed over a cylindrical surface: In which Lw’ is the sound power level per meter of line source

32 Coherent cylindrical field
The power is dispersed over an infinitely long cylinder: L r In which Lw’ is the sound power level per meter of line source

33 “discrete” (and incoherent) linear source
Another common case is when a number of point sources are located along a line, each emitting sound mutually incoherent with the others: Geomtery of propagation for a discrete line source and a receiver We could compute the SPL at teh received as the energetical (incoherent) summation of many sphericla wavefronts. But at the end the result shows that SPL decays with the same cylndrical law as with a coherent source: The SPL reduces by 3 dB for each doubling of distance d. Note that the incoherent SPL is 2 dB louder than the coherent one!

34 Example of a discrete line source: cars on the road
Distance a between two vehicles is proportional to their speed: In which V is speed in km/h and N is the number of vehicles passing in 1 h The sound power level LWp of a single vehicle is: Constant up to 50 km/h Increases linearly between 50 km/h and 100 km/h (3dB/doubling) Above 100 km/h increases with the square of V (6dB/doubling)

35 Example of a discrete line source: cars on the road
Hence there is an “optimal” speed, which causes the minimum value of SPL, which lies around 70 km/h Modern vehicles have this “optimal speed” at even larger speeds, for example it is 85 km/h for the Toyota Prius

36 Outdoors propagation – excess attenuation

37 Free field: excess attenuation
Other factors causing additional attenuation during outdoors progation are: air absorption absorption due to presence of vegetation, foliage, etc. metereological conditions (temperature gradients, wind speed gradients, rain, snow, fog, etc.) obstacles (hills, buildings, noise barriers, etc.) All these effects are combined into an additional term L, in dB, which is appended to the free field formula: LI = Lp = LW - 20 log r log Q - L (dB) Most of these effects are relevant only at large distance form the source. The exception is shielding (screen effect), which instead is maximum when the receiver is very close to the screen

38 Excess attenuation: temperature gradient
Figure 1: normal situation, causing shadowing Shadow zone

39 Excess attenuation: wind speed gradient
Vectorial composition of wind speed and sound speed Effect: curvature of sound “rays”

40 Excess attenuation: air absorption
Air absorption coefficients in dB/km (from ISO standard) for different combinations of frequency, temperature and humidity: Frequency (octave bands) T (°C) RH (%) 63 125 250 500 1000 2000 4000 8000 10 70 0,12 0,41 1,04 1,93 3,66 9,66 32,8 117,0 15 20 0,27 0,65 1,22 2,70 8,17 28,2 88,8 202,0 50 0,14 0,48 2,24 4,16 10,8 36,2 129,0 80 0,09 0,34 1,07 2,40 4,15 8,31 23,7 82,8 1,13 2,80 4,98 9,02 22,9 76,6 30 0,07 0,26 0,96 3,14 7,41 12,7 23,1 59,3

41 Excess attenuation – barriers

42 Noise screens (1) A noise screen causes an insertion loss L: L = (L0) - (Lb) (dB) where Lb and L0 are the values of the SPL with and without the screen. In the most general case, there arey many paths for the sound to reach the receiver whne the barrier is installed: diffraction at upper and side edges of the screen (B,C,D), passing through the screen (SA), reflection over other surfaces present in proximity (building, etc. - SEA).

43 Noise screens (2): the MAEKAWA formulas
If we only consider the enrgy diffracted by the upper edge of an infinitely long barrier we can estimate the insertion loss as: L = 10 log (3+20 N) for N>0 (point source) L = 10 log (2+5.5 N) for N>0 (linear source) where N is Fresnel number defined by:  N = 2 / = 2 (SB + BA -SA)/  in which  is the wavelength and  is the path difference among the diffracted and the direct sound.

44 Maekawa chart

45 Noise screens (3): finite length
If the barrier is not infinte, we need also to soncider its lateral edges, each withir Fresnel numbers (N1, N2), and we have: L = Ld - 10 log (1 + N/N1 + N/N2) (dB) Valid for values of N, N1, N2 > 1. The lateral diffraction is only sensible when the side edge is closer to the source-receiver path than 5 times the “effective height”. heff R S

46 The insertion loss value depends strongly from frequency:
Noise screens (4) Analysis: The insertion loss value depends strongly from frequency: low frequency  small sound attenuation. The spectrum of the sound source must be known for assessing the insertion loss value at each frequency, and then recombining the values at all the frequencies for recomputing the A-weighted SPL. SPL (dB) No barrier – L0 = 78 dB(A) Barrier – Lb = 57 dB(A) f (Hz)

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Putin ordered effort to influence US presidential election

Moscow: Russian President Vladimir Putin ordered an “influence campaign” aimed at hurting Hillary Clinton and helping Donald Trump win in the 2016 presidential election, the US intelligence has revealed in a unclassified report.

The 25-page report released on Friday was the first official, full and public accounting by the US intelligence community of its assessment of Russian cyber hacking activities during the 2016 campaign and the motivations behind that hacking, CNN reported.

The report said Moscow used a variety of tactics in a bid to sway the outcome.

The US intelligence community also released several new pieces of information to support its conclusions, CNN noted.

It noted that in the final run-up to the election, when majority of the polls favoured Clinton to win the election, Moscow shifted its campaign to influence the election to one aimed at undermining the validity of the electoral results.

“Before the election, Russian diplomats had already publicly denounced the US electoral process and were prepared to publicly call into question the validity of the results,” the report stated, adding that pro-Russian government bloggers had prepared a Twitter campaign on Election Night using the hashtag “#DemocracyRIP”.

President-elect Donald Trump was briefed earlier on Friday on the report by top US intelligence and law enforcement officials, and while he said he had “a constructive meeting”, he declined to publicly agree with their conclusions.

Instead, Trump stressed that “there was absolutely no effect on the outcome whatsoever”.

Trump did acknowledge in his statement the possibility that Russia could have been behind the hack, though he named China as well as a persistent cyberhacker.

However, there was no immediate response from Russian officials, although they have denied all the hacking claims, CNN said.

The US intelligence community also warned in its report that Moscow would likely continue to pursue cyberhacking campaigns to influence future elections.

“Moscow will apply lessons learned from its Putin-ordered campaign aimed at the US presidential election to future influence efforts worldwide, including against US allies and their election processes,” it added.

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Live Graphic Recording for Water For People

What a great morning I had creating this map for Water For People! This is a terrific organization whose mission is that EVERYONE has access to safe water FOREVER, and by 2018. It's a lofty goal, but I believe they'll do it. Water For People is well-known nationally and internationally, yet they aren't well-known in Colorado, where they're based. So they asked Denver's top thought leaders to come together for 90 minutes and help them to come up with ideas around how to be more visible in Colorado. It was my pleasure to graphic record this 90-minute session for them.


Now, a Camera Which can Click 3D Pics from a Km Away

LONDON: Researchers have developed a new laser powered camera system that creates high-resolution 3D images of objects from up to a kilometre away. A standard camera takes flat, 2D pictures. To get 3D information, such as the distance to a far-away object, scientists can bounce a laser beam off the object and measure how long it takes the light to travel back to a detector.

The technique, called time-of-flight (ToF) navigation systems for autonomous vehicles, and other applications , but many current systems have a relatively short range and struggle to image objects that do not reflect laser light. Researchers have tackled these limitations and reported their findings in the journal Optics Express.

The research team, led by Gerald Buller, professor at Heriot-Watt University in Edinburgh, Scotland, describes a ToF imaging system that can gather high-resolution , 3D information about objects that are typically very difficult to image, from up to a kilometre away.

The new system works by sweeping a low-power infrared laser beam rapidly over an object. It records, pixel-bypixel , the round-trip flight time of the photons in the beam as they bounce off the object and arrive back at the source. The system can resolve depth on the millimetre scale over long distances using a detector that can "count" individual photons.

The ability of the new system to image objects like items of clothing that do not easily reflect laser pulses makes it useful in a wider variety of field situations, said Aongus McCarthy, the first author of the study. "Our approach gives a low-power route to the depth imaging of ordinary, small targets at very long range," McCarthy said.

The primary use of the system is likely to be scanning static, human-made targets, such as vehicles. With some modifications to the imageprocessing software, it could also determine their speed and direction.

just in


People in bowling alleys all over the country are interested in how they can exponentially increase their game. If you do not have a lot of experience with bowling but would like to get to know more now would be the perfect time to start. Just like with any sport, bowling is all about understanding the fundamentals and getting better in increments.

Bowling For Dummies (For Dummies (Sports & Hobbies)) [Paperback]Before you can play like the expert players you may encounter in local bowling alleys, it is important that you have a solid grasp of those fundamentals.  To start we will just focus on the fundamentals and go with the straight ball. In due time after you get better you have plenty of time to learn hook shots and work different types of angles.

First thing that people in every single one of those bowling alleys understand is that they must become consistent. Especially when you throw the straight ball, you must start becoming consistent with every throw. This is where practice becomes important. The more you practice, the more natural the throw is going to feel and you are going to quickly realize what the difference is between a good throw and a mediocre one.

BSI Ladies 651 Black and Pink Bowling ShoesHowever, as said before, you must understand the fundamentals of the game. This means you are going to have to work on your delivery and how many steps you want to take before you release the ball. This depends on what is most comfortable and feels natural to you, this can depend on such things as the length of your legs. There is a difference between a person taking a three-step approach and those that take five-step approach. You will be amazed at how much the shot speed is going to be affected by just two small steps.

Brunswick Slingshot Bowling Package- Black and SilverNext, focus on the release of the bal. This is very important to the overall quality of your shot and will not only determine where your ball is going to end up, but also how it rolls there. Especially beginning players have a tendency to release their ball early, but you want to release the ball after the ball has moved past your left foot (this is assuming you are right handed, if you bowl left handed it would be your right foot). If you have a later release like this, you are going to be able to steer and guide the ball better. Watching beginner release at most bowling alleys is going to tell you that you are not alone in finding this difficult to do in the beginning. Most beginners are going to feel awkward with this at first, but after the first ten times you bowl this way you are going to notice a massive difference in your game.

Brunswick Remove All Ball Cleaner BottlePart of the problem with this is that we cannot give you a single solitary technique or stance that works for everyone, we are all different shapes and sizes and what will work for a 6'4 adult male is not going to work for a 5'3 adult female.

Allow yourself to become comfortable with bowling, your form only becomes important after you have mastered how to throw the straight roll and getting the ball where you want. After that, you are off to show your moves in bowling alleys everywhere.


Cave Dwellers

Cave Dwellers, term used to designate ancient people who occupied caves in various parts of the world. Cave dwellers date generally from that part of the Stone Age called the Paleolithic, which started, according to some authorities, about 2 million years ago. Caves are natural shelters, offering shade and protection from wind, rain, and snow. As archaeological sites, caves are easy to locate and often provide conditions that encourage the preservation of normally perishable materials, such as bone. As a result, the archaeological exploration of caves has contributed significantly to the reconstruction of the human past.

clicca per ingrandire

Wherever caves were available, prehistoric nomadic hunters and gatherers incorporated them into the yearly cycle of seasonal camps. Most of their activities took place around campfires at the cave mouth, and some caves contain stone walls and pavements providing additional protection from winds and dampness. Hunting, particularly of reindeer, horse, red deer, and bison, was important; many caves are situated on valley slopes providing views of animal migration routes.

The Variety of Artifacts

Artifacts have been found in caves in France, Spain, Belgium, Germany, Italy, and Great Britain. The association of these remains with the bones of extinct animals, such as the cave bear and saber-toothed tiger, indicates the great antiquity of many of the cave deposits.

punto.gif (167 byte)variety of stone

(see photo) and bone points discovered in excavated caves documents the importance of spears until the bow and arrow appeared in the late Paleolithic era. Other common tools included stone scrapers for working hides and wood, burins for engraving, and knives for butchering and cutting. Throughout the Paleolithic period such tools became increasingly diverse and well made. Bone needles, barbed harpoons, and spear-throwers were made and decorated with carved designs. Evidence of bone pendants and shell necklaces also exists. Among the caves that have yielded relics of early humans are the Cro-Magnon and Vallonnet in France.

Wall paintings and engravings have been found in more than 200 caves, largely in Spain and France, dating from 25,000 to 10,000 years ago. Frequently found deep inside the caves, the paintings depict animals, geometric signs, and occasional human figures. In the cave of La Colombi�re in France, a remarkable series of sketches engraved on bone and smoothed stones was unearthed in 1913. In caves such as Altamira in Spain and Lascaux in France, multicolored animal figures were drawn using mineral pigments mixed with animal fats. Some of the paintings adorn walls of large chambers suitable for ritual gatherings; others are found in narrow passages accessible only to individuals. Hunting and fertility seem to have been important artistic themes. The ritual gatherings themselves promoted communication and intermarriage among the normally scattered small groups.

On every continent, prehistoric foragers made use of caves. Chinese caves contain some of the earliest evidence of human use of fire, approximately 400,000 years ago. In the Zhoukoudian (Chou-k'ou-tien) Cave near Beijing, remains of bones and tools of Homo erectus (Peking Man) have been discovered. In the Shandar Cave in Iraq, 50,000-year-old Neandertal skeletons were unearthed in 1957. Ancient pollen buried with them has been interpreted as evidence that these cave dwellers had developed funeral rituals. In the western deserts of North America, caves have been located that contain plant foods, woven sandals, and baskets, representing the desert culture of 9000 years ago. Early inhabitants of Australia, the Middle East, and the Peruvian Andes have also left remains in caves.

Gradually people learned to grow food, rather than forage for it. This was the beginning of the Neolithic age, which, although ending in western Europe some 4500 years ago, continued elsewhere in the world until modern times. Once agriculture became important, people established villages of permanent houses and found new uses for caves, mainly as hunting and herding campsites and for ceremonial activities. In Europe, Asia, and Africa caves continued to be used as shelters by nomadic groups.

Preservation in Caves

In dry caves, preservation is often excellent, due to moistureless air and limited bacterial activity. Organic remains such as charred wood, nutshells, plant fibers, and bones sometimes are found intact. In wet caves, artifacts and other remains often are found encrusted with, or buried beneath, calcareous deposits of dripstone. The collected evidence of human habitation on the cave floor was often buried under rockfalls from the ceilings of caverns. Intentional burials have also been found in a number of cave sites.

Because of the unusual preservative nature of caves and the great age of many of the remains found in them, the fallacious belief has arisen that a race of cave people existed. Actually, most cave sites represent small, seasonal camps. Because prehistoric people spent much of the year in open-air camps, the caves contain the remains of only part of a group's total activities. Also, the cultural remains outside caves were subject to greater decay. Thus, the archaeological record of remote times is better seen in cave deposits.

Caves have been systematically excavated during the past one hundred years. Since they often contain the remains of repeated occupations, caves can document changing cultures. For example, the economic transition from food collecting to agriculture is demonstrated by finds in highland Mexico and in Southeast Asia. Some caves in the Old World continued to be inhabited even after the close of the Stone Age; relics from the Bronze and Iron ages have been found in cave deposits. On occasion, material dating from the time of the Roman Empire has been recovered. The famous Dead Sea Scrolls, discovered in 1947, were preserved in caves.

  stone tool


Design, User Experience
About This Project

I was very fortunate to work with some talent designers  on a project that was developed in collaboration with the Open Societies Foundation(OSF), Parson’s New School, and CEGSS . OSF’s goal is to create works that help hold government agencies accountable through the dissemination of information to the people.   For this project my team mates and I designed a mobile application that uses simple cell phones and a text messaging system(SMS) that allowed medical professionals and patients to request aid and also providing a collection of data to be used per medical facility and the government. The app allowed for aid and supplies to be requested via text messaging using  inventory codes. Using these codes, was the best way to usurp language barriers across the country as many regions do not communicate easily because of regional dialects and language differences.  The data collection website that worked in conjunction with the SMS service provided a democratic data set that both the public and the government could view and promote accountability in all regards to the transportation of medical supplies. For example, if the government fails to provide aid to a medical facility in a timely manner that data is easily viewable by the public online and transversely this real time data provides a means for the government to asses which facilities need supplies and when.

The SMS System:

We have designed a numerical coding system that devotes a code per inventory item and various medical codes. A user must simply just text these numbers to request supplies or aid. A well designed instructional pamphlet has also been designed to accompany the cell phone system. In the precedence image you will notice, that first we experimented with the idea of having a code wheel that would be more portable but found this design to be cumbersome, confusing to users, and less cost effective. So in end we decided that a simple and familiar instructional pamphlet would suffice.

Ushahidi :

Ushahidi is an open source data collection platform, that allows anyone to upload information and gps data that is readily available to anyone online. We decided to use this platform both for its easily accessible api but also because Ushahidi’s mission statement aligns well with our cause.

Take Aways :

While working with a team of very talent designers, I was fortunate to have the opportunity to develop several new skills. Firstly was learning how to set up and develop for an SMS system where text messages were sent to a responding web server.  After being collected on the server they were compared to a registry of data that was then deployed on Ushahidi’s website using it’s api.  In addition to this, we conducted several user testing workshops with our end users. Having the opportunity to discuss the workflow and system we had designed opened my eyes to not only cultural differences and use cases that had not occurred to me but helped us to improve our design and ready it to be used in the field. Lastly, working within a team is always rewarding in itself. Especially on such a humanitarian project such as this.


Nima Sheikhy

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