Department of Nuclear Chemistry, Czech Technical University in Prague, Prague 115 19, Czech Republic.
Department of Radioelectronics, Czech Technical University in Prague, Prague 166 27, Czech Republic.
J Acoust Soc Am. 2022 Sep;152(3):1660. doi: 10.1121/10.0013992.
The basilar membrane in the cochlea can be modeled as an array of fluid coupled segments driven by stapes vibration and by the undamping nonlinear force simulating cochlear amplification. If stimulated with two tones, the model generates additional tones due to nonlinear distortion. These distortion products (DPs) can be transmitted into the ear canal and produce distortion-product otoacoustic emissions (DPOAEs) known to be generated in the healthy ear of various vertebrates. This study presents a solution for DPs in a two-dimensional nonlinear cochlear model with cochlear roughness-small irregularities in the impedance along the basilar membrane, which may produce additional DPs due to coherent reflection. The solution allows for decomposition of various sources of DPs in the model. In addition to the already described nonlinear-distortion and coherent-reflection mechanisms of DP generation, this study identifies a long-latency DPOAE component due to perturbation of nonlinear force. DP wavelets that are coherently reflected due to impedance irregularities travel toward the stapes across the primary generation region of DPs and there evoke perturbation of the nonlinear undamping force. The ensuing DP wavelets have opposite phase to the wavelets arising from coherent reflection, which results in partial cancellation of the coherent-reflection DP wavelets.
耳蜗中的基底膜可以建模为一系列流体耦合段，由镫骨振动和模拟耳蜗放大的未阻尼非线性力驱动。如果用两个音刺激，模型会由于非线性失真而产生附加音。这些失真产物（DP）可以传入耳道，并产生已知在各种脊椎动物健康耳中产生的失真产物耳声发射（DPOAE）。本研究提出了一种在二维非线性耳蜗模型中处理 DP 的解决方案，该模型考虑了耳蜗粗糙度——基底膜上的阻抗小不规则性，这可能由于相干反射而产生额外的 DP。该解决方案允许对模型中的各种 DP 源进行分解。除了已经描述的非线性失真和 DP 产生的相干反射机制外，本研究还由于非线性力的扰动而识别出长潜伏期 DPOAE 分量。由于阻抗不规则而相干反射的 DP 波瓣会沿 DP 的主要产生区域朝向镫骨传播，并在那里引起非线性非阻尼力的扰动。由此产生的 DP 波瓣与来自相干反射的波瓣相位相反，这导致相干反射 DP 波瓣的部分抵消。
