An experimental study of acoustic scattering from thermocline in shallow sea

I.IntroductionThetemperature,salinityandstaticprcssureofscawaterchangewithdepth,whichformsthcsoundvelocityvertica1distributioninthesea.Duringsummcrscason,thercaren0n-uniformthermoclinelaycrsinthedepths0fshallowseaal0ngChinacoast.Wearenowabletodeducctheimpedanccproflle(pc)byechoesofacousticwavesfr0mvarioustherm0c1ine1ayers.Thewaterdcnsityvaricsonlyslight1y,hencetheac0usticve1ocityde-Pendsmainlyonthetemperatureofseawatcr,andthercfore,itispossiblctorecordthcdepthofthermoclinelaycrsbyusingacoust…

An experimental study of acoustic scattering from thermocline in shallow sea

This work was done in Summer of 1988, 1989 and 1992, at three different stations (34, 39 and 44 m under sea level), in the south Yellow Sea using narrow band acoustic pulses with center frequencies of 120, 160 and 200 kHz.The pulses were echoed back from three different depths. We used CTD to record the temperature and salinity of different depth day and night, and the plankton samples at different layers were hauled up for comparison. We applied the numerical method introduced by R. Kind to calculate reflected plane wave spectrum, measured temperature and salinity in vertical direction of non-uniform layer distribution and obtained the numerical simulation signals of backward scattering sound waves from thermocline layers. We then compared them with the experimental data. Through the experiments of the same periords of three years we have confimed that the measured time that layer-scattering-waves to reach our recorders agreed well with that obtained by temperature sectional simulated data. On the other hand, there is no apparent effects of plankton distribution. This indicates that acoustic scattering mainly depends on physical non-uniformity property of the media (sea water).