Effect of an air-back cavity on the sound field reflected by a vibrating plate

The effect of an air-back cavity on the spherical wave reflected by the stage floor is analyzed theoretically. An air-cavity backed infinite elastic plate is driven to vibration by a point force. A closed form expression for the far-field solution is derived by coupling the Helmholtz integrals for sound field and the equation of the plate motion. Numerical examples demonstrate four main features of the sound field. Two of them are absent for the plate without the air-cavity: one is a panel absorption dip owing to the plate and air-cavity resonance system. The other is small peaks and dips due to the acoustic resonances of the air-cavity. (C) 1998 Elsevier Science Ltd. All rights reserved.