Space-frequency distribution of the vector field of broad-band sound in shallow water

An uniform distribution often appears in the space-frequency plane for broad-band, low-frequency sound intensity generated by a moving source in a shallow water environment. Waveguide invariant theory is used to interpret this phenomenon, and it has been applied for inverse problems in underwater acoustics. A vector sensor has advantages in providing both pressure and particle velocity information about the sound field simultaneously, and a higher signal-to-noise ratio signal than a traditional hydrophone. In the present paper, the space-frequency distribution of broad-band vector acoustic signals in a Pekeris waveguide is investigated using normal mode theory. A comparison between experimental and predicted space-frequency distributions is made for the Yellow Shark environment. The effects of the sound speed profile of the water column, the existence of a soft sediment layer, the change of sound speed or thickness of the soft sediment on the space-frequency distribution are examined. The possibility of using space-frequency distributions to invert for environmental parameters is discussed.