Acoustodynamics of the Longitudinal Collinear Impact of Finite Elastic Cylinders

The acoustodynamics of finite elastic cylinders is examined both experimentally and theoretically to investigate the sources of noise generation associated with longitudinal, collinear impact. Analytical predictions are based on the assumption that the acoustic radiation is predominately derived from the acceleration response of the free, plane-end surfaces of the colliding bodies and consists of rigid-body deceleration and vibration “ringing” components. Those predictions are in excellent agreement with structural acceleration and acoustic pressure measurements obtained experimentally from two separate cylinder impact configurations, except for the presence of a single dominant noise pattern originating from the proximity of the impact surfaces. This unexpected noise consists of damped pressure oscillations at a frequency unrelated to any natural frequencies of the test apparatus. Its source can be traced to the injection of air into the region between the impact surfaces just following impact separation.