修正耳蜗模型的短波效应,提升对声音强度变化的模拟精度。
Short-wave admittance correction for a time-domain cochlear transmission line model
- 用自回归滤波与回归技术在时域修正基底膜导纳,引入二维效应。
- 模型增益提升5分贝,压缩动态范围扩展10分贝,频率选择性更稳定。
- 适合研究耳蜗非线性机制或需高保真听觉建模的学者。
时域传输线(TL)模型能高效模拟基底膜(BM)对瞬态或非平稳声音的位移响应。但真实耳蜗存在更高维效应,如压力聚焦和横向黏滞阻尼,尤其在短波区域显著。这些效应依赖波长,更适合在频域描述。本文提出一种数值修正方法,在时域通过自回归滤波与回归技术调整基底膜导纳,以体现二维效应。该修正用于适配沙鼠耳蜗生理特性的模型。原模型因瞬时非线性(可变阻尼)导致声强增加时压缩不足,源于一维非线性模型中增益与频率选择性强耦合,而小哺乳动物耳蜗的频率选择性仅中度随声强变化。引入反馈回路使修正因子具有强度依赖性后,模型实现增益与选择性的部分解耦,获得5分贝额外增益,并将压缩区声强范围拓展10分贝。本文强调两项关键贡献:结合解析与回归方法表征基底膜导纳,以及融合瞬时与非瞬时非线性机制。
原文摘要 · Abstract (English)
Transmission line (TL) models implemented in the time domain can efficiently simulate basilar-membrane (BM) displacement in response to transient or non-stationary sounds. By design, a TL model is well-suited for an one-dimensional (1-D) characterization of the traveling wave, but the real configuration of the cochlea also introduces higher-dimensional effects. Such effects include the focusing of the pressure around the BM and transverse viscous damping, both of which are magnified in the short-wave region. The two effects depend on the wavelength and are more readily expressed in the frequency domain. In this paper, we introduce a numerical correction for the BM admittance to account for 2-D effects in the time domain using autoregressive filtering and regression techniques. The correction was required for the implementation of a TL model tailored to the gerbil cochlear physiology. The model, which includes instantaneous nonlinearities in the form of variable damping, initially presented insufficient compression with increasing sound levels. This limitation was explained by the strong coupling between gain and frequency selectivity assumed in the 1-D nonlinear TL model, whereas cochlear frequency selectivity shows only a moderate dependence on sound level in small mammals. The correction factor was implemented in the gerbil model and made level-dependent using a feedback loop. The updated model achieved some decoupling between frequency selectivity and gain, providing 5 dB of additional gain and extending the range of sound levels of the compressive regime by 10 dB. We discuss the relevance of this work through two key features: the integration of both analytical and regression methods for characterizing BM admittance, and the combination of instantaneous and non-instantaneous nonlinearities.
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