Chirp sonar inversion results from SWAT East China Sea and New Jersey Shelf experiments

Subbottom surveys have been conducted during recent shallow water acoustic technology (SWAT) experiments to invert bottom geoacoustic properties at the East China Sea and New Jersey Shelf sites. Sediment properties such as density, porosity, and sound-speed profiles are inverted by using reflection amplitude and phase data obtained from a hull-mounted 2- to 12-kHz chirp sonar, a deep-towed 2- to 12-kHz chirp sonar, and a 30-kHz acoustic sediment classifier system. The attenuation coefficient is estimated using the frequency shift method which seems to be relatively insensitive to reflection and transmission effects, source-receiver beam patterns, and instrument responses. All three systems provided high-quality reflection data and inversion results are in agreement with those of sediment core measurements. [Work supported by ONR and JDA.]