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Transmission loss patterns from acoustic harassment and deterrent devices do not always follow geometrical spreading predictions
Author(s) -
Shapiro Ari D.,
Tougaard Jakob,
Jørgensen Poul Boel,
Kyhn Line A.,
Balle Jeppe Dalgaard,
Bernardez Cristina,
Fjälling Arne,
Karlsen Junita,
Wahlberg Magnus
Publication year - 2009
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2008.00243.x
Subject(s) - acoustics , range (aeronautics) , sound transmission class , decibel , sound (geography) , harassment , sound exposure , acoustic sensor , interference (communication) , environmental science , multipath interference , multipath propagation , geology , computer science , telecommunications , channel (broadcasting) , physics , engineering , psychology , social psychology , aerospace engineering
Acoustic harassment and deterrent devices have become increasingly popular mitigation tools for negotiating the impacts of marine mammals on fisheries. The rationale for their variable effectiveness remains unexplained, but high variability in the surrounding acoustic field may be relevant. In the present study, the sound fields of one acoustic harassment device and three acoustic deterrent devices were measured at three study sites along the Scandinavian coast. Superimposed onto an overall trend of decreasing sound exposure levels with increasing range were large local variations in the sound level for all sources in each of the environments. This variability was likely caused by source directionality, inter‐ping source level variation and multipath interference. Rapid and unpredictable variations in the sound level as a function of range deviated from expectations derived from spherical and cylindrical spreading models and conflicted with the classic concept of concentric zones of increasing disturbance with decreasing range. Under such conditions, animals may encounter difficulties when trying to determine the direction to and location of a sound source, which may complicate or jeopardize avoidance responses.