Applying the dynamic soundscape to estimates of signal detection

Abstract

The field of underwater acoustics is currently struggling with how to define and apply the concept of a soundscape, which originated for use in the terrestrial environment, to the underwater environment. Sound (especially low frequency sound) travels greater distances underwater compared to in air, so sources from 1000s of kilometers away have the potential to significantly contribute to local soundscapes. Understanding the source contributions within a local soundscape can therefore be complex. In applying our understanding of the soundscape to signal detection, sound level trends, or noise impacts, it is first necessary to parameterize the acoustic environment. This work examines the impact of the dynamic soundscape and selected sound level parameters on estimates of signal detection area, also referred to as active acoustic space when considering effective acoustic communication between vocalizing animals. The range of signal detection was investigated at three site locations of the Comprehensive Nuclear Test- Ban Treaty Organization International Monitoring System. Transmission loss to each hydrophone was computed using the OASIS Peregrine parabolic equation model for a source within the upper 300m of the water column to be consistent with the location of vocalizing baleen whales. Daily, monthly, and seasonal soundscape measurements were incorporated into the sonar equation to estimate the variability in signal detection area as a function of sound level and time.