ASA 127th Meeting M.I.T. 1994 June 6-10

4pEA1. Multipath signal modeling for electroacoustic transducer calibration in reverberant underwater environments.

Phillip L. Ainsleigh

Naval Res. Lab., Underwater Sound Reference Detachment, Orlando, FL 32856-8337

James D. George

Signalmetrics, Inc., Winter Park, FL 32789-5656

A new method was developed for modeling acoustic signals in reverberant environments for application to underwater electroacoustic transducer calibration. Specifically, a multipath exponential model was used to represent the response signals encountered during stepped-sinusoid testing of transducers in bounded test facilities. In these tests, the received signal is the hydrophone's response to the acoustic wave emitted by the projector and traversing both the direct and the reflected propagation paths from the projector to the hydrophone. By modeling the response to both the direct and reflected waves, the desired echo-free steady-state response can be determined from the estimated model parameters corresponding to the earliest arrival time. The method was applied to calibrating a low-frequency high-power tonpilz projector in a small pressurized tank where the echo-free time is shorter than the transient response of the projector. The estimated results agree very closely with measurements made in a large lake where the echo-free steady state can be observed directly. [Work supported by ONR.]