The Research on Measuring the Coefficient of Sound Absorption in Turbid Seawater

When naval mine-hunting sonars and side-scan surveying sonars operating at 20~60 kHz are working in shallow coastal waters, the visco-thermal absorption of sound by suspended mud in the water may greatly decrease their detection properties. This kind of water is also characterized as turbid seawater. However, the research on measuring the coefficient of sound absorption in turbid seawater has little been done. The main difference between turbid seawater and clear seawater is that there are mud particles suspending in turbid seawater. It is also the main reason why sound absorption in turbid seawater is greater than that in clear seawater. In the paper, the coefficient of sound absorption at 20~60 kHz in turbid seawater has been measured by the reverberation technique. Results demonstrate that if the concentration of the mud is bellow 0.11 kg per cubic meters, the mud in turbid seawater doesn’t cause additional absorption. When the concentration of the mud is between 0.14 and 0.49 kg per cubic meters, the coefficient of sound absorption in turbid seawater is as twice at least as that in clear seawater.