Analysis of transient sound energy flow in impact noise

The formative mechanism and characteristics of the initial transient sound field caused by the transient vibration response of a clamped circular plate are analyzed using an external point force with a squared half-period sine-wave time history. The dynamic and acoustic responses of a circular plate are expressed by using both the dimensionless parameter beta introduced by the group velocity of the dominant frequency component and the dimensionless parameter gamma introduced by the sound speed in the acoustic medium. From the analysis the following results were obtained. First, the propagation of kinetic energy can be seen by observing the period from about 0 to 2/beta. Second, dimensionless sound energy radiation patterns from the plate rely on beta. Third, the maximum instantaneous sound intensity on the axis of symmetry is formed by sound radiated from principal modal bending waves which are reflected at the edge of the circular plate.