I have been doing some research on all kinds of sound-related topics lately and have been a bit confused by the different uses of the term "frequency". Of course, the most general meaning of frequency is just how many times something happens during a certain period of time (a second, usually). However, I've also come across many texts referring to a sound containing multiple frequencies, which seemed weird to me at first. Now, after reading up on stuff like Fourier analysis I've come to understand that "frequencies" in this case refers to the frequencies of the sine waves that make up the sound. So I guess my question comes down to this:
- Is the above correct, or am I still not understanding it correctly in some way?
- Assuming it is, is this not pretty ambiguous terminology? You could for example say that a square wave with a frequency of 440 Hz (meaning the waveform repeats 440 times per second) consists of many different frequencies (meaning it consists of many sine waves with different frequencies). It's not hard to see how this could be confusing.
- And in that case, why can I not easily find a clear explanation of this anywhere? It took me quite some time to piece this together myself and seems like it really should be pretty basic stuff. For example, I first really started thinking about this when I ran into the Nyquist frequency. It seemed logical to me that you needed at least two samples per period to represent any kind of change, so the maximum frequency of the signal could only be half of the sampling rate, but when I started involving different kind of waveforms I realized there would be no way to distinguish between them. It took me a lot of time to figure out that the Nyquist frequency implicitly refers to the maximum frequency that any sine wave present in the signal could have, making it impossible to sample any other waveform at the Nyquist frequency.
Of course, if anyone could explain or point me in the direction of some material explaining the importance of sine waves in a more general fashion, and why these things seem to be supposed to be so obvious, that would be appreciated, but the three questions above are what I'm really wondering about.