Introduction: In order to understand human hearing, it helps to understand how the ears of lower vertebrates, like, for instance, lizards, function. A key feature in common is that the ears of both humans and lizards emit faint, pure tones known as spontaneous otoacoustic emissions (SOAEs). More than four decades after their discovery, the mechanism underlying these emissions is still imperfectly understood, although it is known that they are important for improving the sensitivity and sharpness of hearing. In both humans and lizards, the frequencies of SOAEs change by a few percent when static pressure is applied to the tympanic membrane. For the human ear, this observation is normally explained by a so-called global oscillator model (such as with Shera’s coherent reflection model), in which the emissions result from standing waves, and external pressure changes the boundary conditions – the stiffness of the oval and round windows – which then has a global effect on the SOAE frequencies. Methods: Here we investigate how changing parameters of an earlier developed local oscillator model for the lizard ear can change the frequencies of the SOAEs. A major feature of the model is that each oscillator is coupled only to its immediate neighbours. The oscillators then cluster into groups of identical frequency, and each of these so-called frequency plateaus can be taken to represent an SOAE. Results: Even though the natural (unperturbed) frequencies of all the oscillators remain fixed, here we find for several model parameters that by slightly changing their value the frequency plateaus – the SOAEs – shift by a few percent. Plots of how these changes alter SOAE frequencies are given, and their magnitude corresponds well with observations of SOAE changes in lizards. Discussion: Investigation of the influence of the change of parameters in an earlier developed local oscillator model for the lizard ear shows that a local oscillator model can explain small SOAE frequency changes as well as a global oscillator model.
Audiol Neurotol

中文翻译：

---

蜥蜴耳产生自发耳声发射的本地振荡器模型中的频移

介绍：为了了解人类的听力，有助于了解低等脊椎动物（例如蜥蜴）的耳朵如何运作。一个关键的共同特征是人类和蜥蜴的耳朵都会发出微弱的纯音，称为自发耳声发射（SOAE）。在它们被发现四十多年后，人们仍然不完全了解这些发射的机制，尽管众所周知它们对于提高听力的灵敏度和清晰度很重要。当对鼓膜施加静压时，人类和蜥蜴的 SOAE 频率都会发生几个百分点的变化。对于人耳来说，这种观察结果通常可以用所谓的全局振荡器模型（例如 Shera 的相干反射模型）来解释，其中发射来自驻波，方法：在这里，我们研究改变早期开发的蜥蜴耳朵本地振荡器模型的参数如何改变 SOAE 的频率。该模型的一个主要特征是每个振荡器仅与其直接相邻的振荡器耦合。然后，振荡器聚集成具有相同频率的组，并且每个所谓的频率平台都可以用来表示 SOAE。结果：尽管所有振荡器的自然（未受扰动）频率保持固定，但我们发现，对于几个模型参数，通过稍微改变其值，频率平台（SOAE）会移动几个百分点。给出了这些变化如何改变 SOAE 频率的图，其幅度与蜥蜴 SOAE 变化的观察结果非常吻合。讨论：对早期开发的蜥蜴耳本地振荡器模型中参数变化的影响的研究表明，本地振荡器模型可以解释小的 SOAE 频率变化以及全局振荡器模型。
音频神经托尔