U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center, San Diego, CA 92152, USA.
J Acoust Soc Am. 2011 Aug;130(2):1038-48. doi: 10.1121/1.3608117.
Measurement of the auditory steady-state response (ASSR) is increasingly used to assess marine mammal hearing. These tests normally entail measuring the ASSR to a sequence of sinusoidally amplitude modulated tones, so that the ASSR amplitude function can be defined and the auditory threshold estimated. In this study, an alternative method was employed, where the ASSR was elicited by an amplitude modulated stimulus whose sound pressure level was slowly varied, or "swept," over a range of levels believed to bracket the threshold. The ASSR amplitude function was obtained by analyzing the resulting grand average evoked potential using a short-time Fourier transform. The suitability of this technique for hearing assessment of bottlenose dolphins and California sea lions was evaluated by comparing ASSR amplitude functions and thresholds obtained with swept amplitude and discrete, constant amplitude stimuli. When factors such as the number of simultaneous tones, the number of averages, and the frequency analysis window length were taken into account, the performance and time required for the swept-amplitude and discrete stimulus techniques were similar. The decision to use one technique over another depends on the relative importance of obtaining suprathreshold information versus the lowest possible thresholds.
测量听觉稳态反应 (ASSR) 越来越多地用于评估海洋哺乳动物的听力。这些测试通常需要测量对一系列正弦幅度调制音调的 ASSR，以便定义 ASSR 幅度函数并估计听觉阈值。在这项研究中，采用了一种替代方法，通过对声压级逐渐变化或“扫频”的幅度调制刺激物来引发 ASSR，扫频范围涵盖了被认为是阈值范围的幅度。使用短时傅里叶变换分析得出的总和诱发电位来获得 ASSR 幅度函数。通过比较使用扫频幅度和离散恒定幅度刺激获得的 ASSR 幅度函数和阈值，评估了该技术用于评估宽吻海豚和加利福尼亚海狮听力的适用性。考虑到同时使用的音调数量、平均值数量和频率分析窗口长度等因素后，扫频幅度和离散刺激技术的性能和所需时间相似。选择使用一种技术而不是另一种技术取决于获得超阈值信息与尽可能低的阈值的相对重要性。
