  Acoustic radiation due to vibration and impact of a spring-mass-damper
oscillator whose motion is constrained by a barrier is analyzed at a field
point in a free field. Impact between the mass and the barrier is modeled using
a coefficient of restitution model. Non-linear behavior of the oscillator is
observed due to motion constraint. Steady state response is studied using a
bifurcation diagram. For small amplitudes of oscillation, the pressure
perturbation by a vibrating mass in a compressible fluid is modeled as an
acoustic dipole with its center at the equilibrium position of the mass and its
axis aligned with the motion of the oscillator. The boundary condition for the
acoustic domain is an acoustic free-field condition. It is observed that the
unsteady acoustic pressure resulting from the impact force is a few orders of
magnitude greater relative to the pressure field resulting from vibration alone
before or after impact. We also analyzed the influence of coefficient of
restitution, damping ratio, the ration of base excitation frequency to the
natural frequency, and the ratio of the distance of the barrier to the base
excitation amplitude on the acoustic radiation. Damping ratio and coefficient
of restituion are shown to be the most significant paramters that affect the
acoustic radiation from the vibro-impact oscillator.
