Pressure Reflection Coefficient Measurement using Echo Sounder with Acoustic Cavitation Noise as Sound Source

An echo sounder employing acoustic cavitation noise as sound source was developed with the aim of realizing a broadband pressure reflection coefficient measurement. This study sought to verify the feasibility of broadband pressure reflection coefficient measurement with this echo sounder. The developed echo sounder used an off-axis parabolic acoustic mirror to shape the spherical shockwaves generated under the ultrasonic horn into plane shockwaves. The plane shockwave irradiated the target. The shockwave was reference-measured on the mirror, and the target range was obtained from the cross-correlation function between the reference signal and the echo. A frequency spectrum of the cross-correlation function was used to determine the pressure reflection coefficient of the target. The results of the verification experiment using an acrylic plate as the target showed that this echo sounder could accurately measure the range. It was also shown that the sound pressure reflection coefficient of the acrylic plate could be measured successfully in the frequency range from 20 kHz to 5 MHz. These results indicate that the echo sounder using acoustic cavitation noise can measure the broadband pressure reflection coefficient, but the current echo sounder setup still has the problem of low correlation between the reference signal and echoes.