Similar susceptibility to temporary hearing threshold shifts despite different audiograms in harbor porpoises and harbor seals.

This article focuses on comparing the susceptibility to temporary hearing threshold shifts (TTS) in harbor seals (Phoca vitulina) and harbor porpoises (Phocoena phocoena) following exposure to anthropogenic noise. Despite substantial differences in their audiograms and hearing sensitivities, both species exhibit similar frequency-dependent susceptibility to TTS, with the greatest vulnerability occurring in the mid-frequency range of approximately 22.5–50 kHz. The study synthesizes data from controlled 1-hour exposures to one-sixth-octave noise bands and continuous tones, revealing that TTS onset occurs at comparable critical sound pressure levels (~145 dB re 1 μPa) in both species. These findings suggest that audiograms alone are insufficient predictors of TTS susceptibility and highlight the importance of considering critical levels and frequency-specific responses when assessing the impact of anthropogenic noise on marine mammal hearing.