Title
Modelling the broadband propagation of marine mammal echolocation clicks for click-based population density estimates
Author
von Benda-Beckmann, A.M.
Thomas, L.
Tyack, P.L.
Ainslie, M.A.
Publication year
2018
Abstract
Passive acoustic monitoring with widely-dispersed hydrophones has been suggested as a cost-effective method to monitor population densities of echolocating marine mammals. This requires an estimate of the area around each receiver over which vocalizations are detected - the "effective detection area" (EDA). In the absence of auxiliary measurements enabling estimation of the EDA, it can be modelled instead. Common simplifying model assumptions include approximating the spectrum of clicks by flat energy spectra, and neglecting the frequency-dependence of sound absorption within the click bandwidth (narrowband assumption), rendering the problem amenable to solution using the sonar equation. Here, it is investigated how these approximations affect the estimated EDA and their potential for biasing the estimated density. EDA was estimated using the passive sonar equation, and by applying detectors to simulated clicks injected into measurements of background noise. By comparing model predictions made using these two approaches for different spectral energy distributions of echolocation clicks, but identical click source energy level and detector settings, EDA differed by up to a factor of 2 for Blainville's beaked whales. Both methods predicted relative density bias due to narrowband assumptions ranged from 5% to more than 100%, depending on the species, detector settings, and noise conditions. © 2018 Acoustical Society of America.
Subject
2015 Observation, Weapon & Protection Systems
AS - Acoustics & Sonar
TS - Technical Sciences
Defence Research
Defence, Safety and Security
Absorption spectroscopy
Acoustic noise
Acoustic wave absorption
Cost effectiveness
Population statistics
Sonar
Sound insulating materials
Spectroscopy
Auxiliary measurements
Broadband propagation
Cost-effective methods
Effective detection areas
Frequency dependence
Passive acoustic monitoring
Population densities
Spectral energy distribution
Mammals
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TNO identifier
787760
ISSN
0001-4966
Source
Journal of the Acoustical Society of America, 143 (2), 954-967
Document type
article