Thresholds for noise induced hearing loss in harbor porpoises and phocid seals
Journal of the Acoustical Society of America|Jakob Tougaard, Kristian Beedholm and Peter T. Madsen|Jun 29, 2022
This important report examines the origins of current noise thresholds that are believed to be sufficiently protective for marine mammals and how little research has actually been conducted to validate these thresholds. The abstract of the report is provided below. The full paper can be downloaded from the document links on this page.
This important report examines the origins of current noise thresholds that are believed to be sufficiently protective for marine mammals and how little research has actually been conducted to validate these thresholds. The abstract of the report is provided below. The full paper can be downloaded from the document links on this page.
Abstract
Intense sound sources, such as pile driving, airguns, and military sonars, have the potential to inflict hearing loss in marine mammals and are, therefore, regulated in many countries. The most recent criteria for noise induced hearing loss are based on empirical data collected until 2015 and recommend frequency-weighted and species group-specific thresholds to predict the onset of temporary threshold shift (TTS). Here, evidence made available after 2015 in light of the current criteria for two functional hearing groups is reviewed. For impulsive sounds (from pile driving and air guns), there is strong support for the current threshold for very high frequency cetaceans, including harbor porpoises (Phocoena phocoena). Less strong support also exists for the threshold for phocid seals in water, including harbor seals (Phoca vitulina). For non-impulsive sounds, there is good correspondence between exposure functions and empirical thresholds below 10 kHz for porpoises (applicable to assessment and regulation of military sonars) and between 3 and 16 kHz for seals. Above 10 kHz for porpoises and outside of the range 3–16 kHz for seals, there are substantial differences (up to 35 dB) between the predicted thresholds for TTS and empirical results. These discrepancies call for further studies.
