Experiment on Effect of Screening Hydrophone for Reduction of Flow-Induced Ambient Noise in Ocean

Abstract

Experimental results, measured in a shallow sea with tidal current for reducing the flow-induced low-frequency ambient noise, are represented. The hydrophone screened with 3-cm-thick 10 ppi open-cell foam showed the reduction of flow-induced ambient noise up to 24 dB below 50 Hz at the current speed of 56 cm/s. The attenuation of acoustic energy caused by the screen, estimated based on the measurements of ship noise in situ and hydrophone sensitivity in a water tank, is considered to be less than 1 dB at 2-10 kHz band when the thickness of the foam is less than 3 cm. (C) 2011 The Japan Society of Applied Physics