Vertical coherence of ambient noise in shallow water

The vertical coherence of wave breaking noise in shallow water is seen to be stable since it is influenced by seabed characteristics and hence can be used for estimating geoacoustic properties of the sea floor. Time series measurements of ambient noise taken at a shallow site of 30 m depth using a Vertical Linear Array (VLA) of hydrophones have been used to estimate coherence. Vertical coherence for the site also has been estimated using a theoretical model developed by Deane et al., 1997 [1]. Geoacoustic properties of the sediment derived based on the sediment type and measured water column sound speed are used in the model. Coherences computed using data and theory have been presented and the results are compared. It is seen that theoretical real and imaginary coherence in the 5 kHz band compares well with real and imaginary coherence from the field measurements.