Center for Applied Hearing Research, Department of Electrical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
J Acoust Soc Am. 2011 Jun;129(6):3797-807. doi: 10.1121/1.3575596.
Two objective measures of human cochlear tuning, using stimulus-frequency otoacoustic emissions (SFOAE), have been proposed. One measure used SFOAE phase-gradient delay and the other two-tone suppression (2TS) tuning curves. Here, it is hypothesized that the two measures lead to different frequency functions in the same listener. Two experiments were conducted in ten young adult normal-hearing listeners in three frequency bands (1-2 kHz, 3-4 kHz and 5-6 kHz). Experiment 1 recorded SFOAE latency as a function of stimulus frequency, and experiment 2 recorded 2TS iso-input tuning curves. In both cases, the output was converted into a sharpness-of-tuning factor based on the equivalent rectangular bandwidth. In both experiments, sharpness-of-tuning curves were shown to be frequency dependent, yielding sharper relative tuning with increasing frequency. Only a weak frequency dependence of the sharpness-of-tuning curves was observed for experiment 2, consistent with objective and behavioural estimates from the literature. Most importantly, the absolute difference between the two tuning estimates was very large and statistically significant. It is argued that the 2TS estimates of cochlear tuning likely represents the underlying properties of the suppression mechanism, and not necessarily cochlear tuning. Thus the phase-gradient delay estimate is the most likely one to reflect cochlear tuning.
已经提出了两种客观的人类耳蜗调谐测量方法，使用刺激频率耳声发射（SFOAE）。一种测量方法使用 SFOAE 相位梯度延迟，另一种测量方法使用双音抑制（2TS）调谐曲线。在这里，假设这两种测量方法在同一听众中会导致不同的频率函数。在三个频率带（1-2 kHz、3-4 kHz 和 5-6 kHz）中，在 10 名年轻成年正常听力听众中进行了两项实验。实验 1 记录了 SFOAE 潜伏期随刺激频率的变化，实验 2 记录了 2TS 等输入调谐曲线。在这两种情况下，输出都基于等效矩形带宽转换为调谐锐度因子。在这两个实验中，调谐锐度曲线都显示出频率依赖性，随着频率的增加，相对调谐变得更加尖锐。实验 2 仅观察到调谐锐度曲线的微弱频率依赖性，与文献中的客观和行为估计一致。最重要的是，两种调谐估计之间的绝对差异非常大且具有统计学意义。有人认为，2TS 估计的耳蜗调谐可能代表抑制机制的潜在特性，而不一定是耳蜗调谐。因此，相位梯度延迟估计最有可能反映耳蜗调谐。
