The separation of multipath reflection waves in water

In the past, the standing wave method was used to we measure the acoustic c haracteristic of underwater objects which Includes complex sound pressure r eflectance, a normal-incident absorption coefficient and normal impedance. The standing wave method is not suitable for performing measurements in a l ow-frequency range, because the length of the sound tube should be at least more than one wavelength. The 2-hydrophone method was proposed to rectify this drawback. But in the 2-hydrophone method, it is necessary to measure t he sound velocity precisely In this study, we inspect the S-hydrophone meth od. where it is nut necessary to measure the velocity of sound in water. We also applied the acoustic intensity method to separate multipath waves in water. We proved successful separation of multipath reflection waves using the 3-hydrophone method and the envelope intensity method. The effectivenes s of those methods was verified.