There is a growing concern in the literature about the effects of low frequency sounds (LFS) on marine mammals. A primary way to assess these effects on marine mammals involves the study of disturbance reactions. Detailed research of disturbance reactions of submerged marine mammals requires 3- dimensional localization and tracking of the animals. Animals such as sperm whales *Physeter macrocephalus* are localized passively with the use of travel time differences (TTD) of their vocalizations received by multiple hydrophones at known positions. Classically, straight-line paths of sound propagation between source and receiver are used to calculate source position. A more accurate calculation of source position involves naturally occurring non- constant sound speeds. This gives rise to arced paths of sound propagation between source and receiver. An algorithm is used to recursively pinpoint source position in a medium with a non-constant sound speed. 5 hydrophone array configurations are tested, each with 30 randomly generated source positions. Average errors of the 150 source position calculations (x, y, z) are (±1.58m, ±1.70m, ±10.44m) for the straight line, and ±0.76m, ±0.87m, ±1.10m) for the algorithm. On average, the algorithm improves the source depth calculation by an order of magnitude.

# Passive Iocalization of acoustic sources in media with non-constant sound velocity ' [abstract]

*Bioacoustics*, Volume 9 (2): 155 -156

Abstract: