Underwater noise can affect the hearing and behavior of marine mammals, as shown in previous research studies (Finneran, 2015). Very loud sounds, such as pile driving, air guns, and military sonars have been shown to inflict hearing loss in marine mammals. As a result, there are regulations in place in many countries limiting noise exposure that may cause a temporary threshold shift (TTS) in marine life, specifically, porpoises and seals. Unfortunately, the most recent guidelines are from 2015 and need updating.
Researchers in Denmark compiled data on TTS onset thresholds (the sound-exposure level required to induce 6 dB of TTS) from the literature. They note that a substantial number of studies of TTS in porpoises and seals have been conducted in recent years and, thus, a large body of empirical data has become available since 2015. The authors also note that there is “substantial interest” from regulatory bodies and other stakeholders regarding the estimated thresholds for TTS onset, as these form the basis of legislation and regulation of noise-generating activities in many countries.
The review of new experimental data for porpoises and seals showed significant discrepancies between newer data and the existing TTS onset thresholds for both mammals. However, the authors reported that the TTS onset thresholds that are currently being used are still conservative enough to protect the hearing of our marine friends from the noise of pile drivers, seismic air guns, and military low- and mid- frequency sonars. Finally, the authors report substantial uncertainties remain regarding the impact of low-frequency noise exposure for seals and high-frequency noise exposure for porpoises and strongly encourage new experiments.
References
Finneran JJ. (2015) Noise-induced hearing loss in marine mammals: a review of temporary threshold shift studies from 1996 to 2015. J Acoust Soc Am 138(3):1702–1726.
Tougaard J, Beedholm K, Madsen PT. (2022) Thresholds for noise-induced hearing loss in harbor porpoises and phocid seals. J Acoust Soc Am 151(6):4252–4263.
Related Posts
Recent Posts
A Virtual Reality System for Delivery of Military-Specific Vestibular Rehabilitation After Mild Traumatic Brain Injury: The Praxis Study Protocol
In an article by Alroumi et al. (2025), treatment of mild traumatic brain injury (mTBI) through the use of virtual reality (VR) system was investigated….
From Capitol Hill to Your Clinic: SPAN July Meeting on Medicaid Cuts
The State Policy Advocacy Network (SPAN) will convene again on July 29 for a critical meeting about Medicaid funding. SPAN brings together nationwide audiologists and…
EHDI Program at Risk
On April 1, President Trump’s administration eliminated the entire branch of the Early Hearing Detection and Intervention (EHDI) program that works with states to analyze…