Acoustic pulse scattering by baffled membranes

Asymptotic expansions as e--,0 that are uniformly valid in t are obtained for the membrane's motion and the scattered acoustic pressure field. The small parameter ß is the density ratio of the acoustic fluid and the membrane. For simplicity of presentation, only plane, compact incident pulses are considered. The scattered field depends on the pulse's tructure. If it is a sufficiently narrow bandwidth pulse which contains none of the in vacuo natural frequencies of the membrane, then it is essentially reflected as though the baffled plane is completely rigid. However, if the pulse spectrum is sufficienfiy broad so that it contains one or more of the in vacuo natural frequencies ofthe membrane, an additional scattered field is produced. This scattered field insonifies distant observation p i ts after the rigidly reflected pulse has arrived. It is the sum of slightly damped and oscillating outgoing spherical waves that represents he "decayed ringing" of the membrane. Application is given to the baffled circular membrane which is insonified by a normally incident pulse. Graphs of the membrane's motion and the farfield acoustic pressure are given. They demonstrate the importance ofthe incident pulse width on the qualitative f atures of the response.