The communication space of humpback whale social sounds in vessel noise

Abstract

This receiver’s detection threshold can be used to define the “communication space” of a signal. If unwanted noise increases, then the size of this space may decrease due to increased signal masking. This, in turn, may have detrimental effects on its ability to obtain important social information. Migrating humpback whales rely on a communication network for social interactions. To generate masking models, and infer communication space in increasing vessel noise, changes in signal-above-noise (SNR) and frequency content of received humpback whale social sounds were modelled with the combined effect of increasing background noise and distance from the source (signaling whales). The signaler distance at which a received signal-to-noise ratio was 0 dB was assumed to be the limit of the communication space. In levels exceeding 110 dB re 1 µPa (vessel within approximately 2.5 km), the received SNR for most vocalizations from a signaler greater than 1 km away was below 0. However, higher frequency vocalizations were generally emitted at lower source levels and therefore had a smaller measured communication space. Comparisons with communication space in wind-dominated noise suggests vessel noise reduced the communication space of vocalizations above that due to typical wind-dominated noise.