Assessing the Possibilities of Identifying Bowhead Whales on the Arctic Shelf

Abstract

Real recordings of bowhead whale signals and numerical simulation were used to investigate the propagation of such signals in an Arctic-type shallow-water waveguide. The authors analyzed attenuation and distortion of whale signals with increasing distance in the following conditions: (1) a soft and hard bottom, (2) different whale depths, (3) surface waves, (4) additive noise, and (5) reception by a single hydrophone and a vertical array. Signal attenuation was estimated by the change in sound pressure level (SPL). Signal distortion was estimated by the change in the correlation coefficient for the spectrograms of received signals and the reference spectrograms. It is shown that, compared to signals from a single receiver, the attenuation and distortion characteristics of the array output signals are more stable and resistant to changes in whale depth, to possible, under Arctic conditions, significant variations in sound speed in the bottom along the acoustic path, and to the effects of additive noise. The results can be used for passive monitoring of bowhead whales on the Arctic shelf.