Transmission Of Sound Through A Randomly Rough Air Sea Interface

Transmission of Sound Through a Randomly Rough Air-sea Interface

Frequency Dependence of Sound Transmitted from an Airborne Source Into the Ocean

The predicted dependence of sound transmission on the statistics of the randomly-rough interface between dissimilar fluids has been studied by use of the Helmholtz Integral. The predictions have been verified for radiation from a helicopter hovering, and slowly moving, over the sea, for frequencies to 1000 Hz for a wide range of slowly moving, over the sea, for frequencies to 1000 Hz for a wide range of surface acoustical roughnesses. The roughness parameters are the rms height of the surface, propagation constant, speed of propagation and angle with the normal, respectively. The transmission change of sound pressure as a function of frequency is presented for several conditions of an SH3-D helicopter hovering and flying over or near an array of microphone and sonobuoy hydrophones. (Author)

Transmission of Sound Through a Randomly Rough Air-Sea Interface

The Helmholtz integral and the Kirchhoff approximation have been used to develop predictions for the transmission of sound through a rough air-sea interface. A model study was conducted with wind-driven surfaces generated in a large anechoic tank. The frequencies used were scaled to be equivalent to low audio frequencies with moderate seas. The coherent component of the transmitted acoustic intensity was tested for exponential decrease with increasing values of the roughness parameter. An empirical correction factor was determined to give a corrected roughness. (Author).