Research Group Experimental Oto-rhino-laryngology (ExpORL), Department of Neurosciences, KU Leuven, Herestraat 49, Box 721, 3000 Leuven, Belgium.
Sea Mammal Research Company (SEAMARCO), Julianalaan 46, 3842 CC Harderwijk, The Netherlands.
J Acoust Soc Am. 2024 Jan 1;155(1):396-404. doi: 10.1121/10.0024343.
When they are exposed to loud fatiguing sounds in the oceans, marine mammals are susceptible to hearing damage in the form of temporary hearing threshold shifts (TTSs) or permanent hearing threshold shifts. We compared the level-dependent and frequency-dependent susceptibility to TTSs in harbor seals and harbor porpoises, species with different hearing sensitivities in the low- and high-frequency regions. Both species were exposed to 100% duty cycle one-sixth-octave noise bands at frequencies that covered their entire hearing range. In the case of the 6.5 kHz exposure for the harbor seals, a pure tone (continuous wave) was used. TTS was quantified as a function of sound pressure level (SPL) half an octave above the center frequency of the fatiguing sound. The species have different audiograms, but their frequency-specific susceptibility to TTS was more similar. The hearing frequency range in which both species were most susceptible to TTS was 22.5-50 kHz. Furthermore, the frequency ranges were characterized by having similar critical levels (defined as the SPL of the fatiguing sound above which the magnitude of TTS induced as a function of SPL increases more strongly). This standardized between-species comparison indicates that the audiogram is not a good predictor of frequency-dependent susceptibility to TTS.
当海洋中的哺乳动物暴露在响亮的使人疲劳的声音中时，它们容易受到听力损伤，表现为暂时听阈偏移（TTS）或永久性听阈偏移。我们比较了具有不同低频和高频听力敏感度的港海豹和港湾海豚对 TTS 的水平和频率依赖性易感性。这两个物种都暴露在占其整个听力范围的 100%占空比的六分之一倍频程噪声带中。对于港海豹的 6.5kHz 暴露，使用了纯音（连续波）。TTS 的定量测量是作为比疲劳声音中心频率高半倍频程的声压级（SPL）的函数。这两个物种的听力图不同，但它们对 TTS 的频率特异性易感性更为相似。这两个物种对 TTS 最敏感的听力频率范围为 22.5-50kHz。此外，这些频率范围的特征是具有相似的临界水平（定义为疲劳声音的 SPL，超过该 SPL 时，TTS 的诱导幅度随 SPL 的增加而更强）。这种种间标准化比较表明，听力图并不是对 TTS 的频率依赖性易感性的良好预测指标。
