Department of Radioelectronics, Czech Technical University in Prague, Technická 2, 166 27 Prague 6, Czech Republic.
Section of Physiological Acoustics and Communication, Department of Otolaryngology, Eberhard-Karls-University Tübingen, Elfriede-Aulhorn-Strasse 5, 72076 Tübingen, Germany.
J Acoust Soc Am. 2019 May;145(5):2909. doi: 10.1121/1.5100611.
Distortion product otoacoustic emissions (DPOAEs) are evoked by two stimulus tones with frequency f and f of ratio f/f in the range between approximately 1.05 and 1.4. This study theoretically and experimentally analyzes the cubic 2f-f DPOAE for different stimulus levels of one of the tones while the other is constant. Simulations for f/f of 1.2 and moderate stimulus levels (30-70 dB sound pressure level) indicate that cubic distortion products are generated along a relatively large length of the basilar membrane, the extent of which increases with stimulus level. However, apical from the place of maximum nonlinear force, the wavelets generated by these distributed sources mutually cancel. Therefore, although the spatial extent of the primary DPOAE sources broadens with increasing stimulus level (up to 1.5 oct), the basilar-membrane region contributing to the DPOAE signal is relatively narrow (0.6 oct) and level independent. The observed dependence of DPOAE amplitude on stimulus level can be well-approximated by a point source at the basilar-membrane place where the largest distortion product (maximum of the nonlinear force) is generated. Onset and offset of the DPOAE signal may contain amplitude overshoots (complexities), which are in most cases asymmetrical. Two-tone suppression was identified as the main cause of these onset and offset complexities. DPOAE measurements in two normal-hearing subjects support the level dependence of the steady-state DPOAE amplitude and the asymmetry in the onset and offset responses predicted by the theoretical analysis.
畸变产物耳声发射（DPOAEs）是由两个刺激频率为 f 和 f 的频率比 f/f 在大约 1.05 和 1.4 之间的刺激产生的。本研究从理论和实验上分析了在一个音调的刺激水平不同的情况下，两个音调的立方 2f-f DPOAE。对于 f/f 为 1.2 和中等刺激水平（30-70dB 声压级）的模拟表明，三次失真产物是沿着基底膜的相对较大长度产生的，其程度随着刺激水平的增加而增加。然而，在最大非线性力的位置上，这些分布源产生的波相互抵消。因此，尽管主要 DPOAE 源的空间范围随着刺激水平的增加而扩大（高达 1.5 倍），但对 DPOAE 信号有贡献的基底膜区域相对较窄（0.6 倍）且与水平无关。观察到的 DPOAE 幅度与刺激水平的依赖性可以通过在基底膜位置处的点源很好地近似，该位置产生最大的失真产物（非线性力的最大值）。DPOAE 信号的起始和结束可能包含幅度过冲（复杂性），在大多数情况下是不对称的。双音抑制被确定为这些起始和结束复杂性的主要原因。两名正常听力受试者的 DPOAE 测量结果支持稳态 DPOAE 幅度的水平依赖性以及理论分析预测的起始和结束响应的不对称性。
