Auditory masking of tonal and conspecific signals by continuous active sonar, amplitude modulated noise, and Gaussian noise in killer whales (Orcinus orca).

This article investigates the auditory masking effects of continuous active sonar (CAS) noise on signal detection in killer whales (Orcinus orca), focusing on both pure tones and natural broadband killer whale calls (KWC). Using behavioral hearing tests with two adult male killer whales, the study found that CAS noise, characterized by a frequency-modulated upsweep with multiple harmonics overlapping killer whale vocalizations, effectively masks communication signals more than Gaussian or amplitude-modulated (AM) noise. While whales employed an off-frequency listening strategy to detect calls masked by Gaussian and AM noise, this strategy was less effective against CAS due to its broadband harmonic structure and reverberation, suggesting CAS could disrupt killer whale communication critical for group coordination. The findings highlight potential negative impacts of CAS on killer whale acoustic behavior despite its lower sound pressure levels compared to pulsed active sonar.