Hsiao Wei-Chen, Chen Yung-Ching, Liu Yi-Wen
Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan.
Front Digit Health. 2021 Sep 1;3:724539. doi: 10.3389/fdgth.2021.724539. eCollection 2021.
The distortion-product otoacoustic emission (DPOAE) is a backward propagating wave generated inside the cochlea during the wave amplification process. The DPOAE signal can be detected rapidly under relatively noisy conditions. In recent years, the earphone industry demonstrated interest in adopting DPOAE as an add-on feature to make their product "intelligent" of inner-ear status. However, a technical challenge remains to be tackled-the loudspeaker in an earphone generates its own cubic distortion at the same frequency as DPOAE. Unfortunately, the intensity of loudspeaker distortion is typically comparable to that of the DPOAE, if not higher. In this research, we propose two strategies, namely and , to enable DPOAE measurement with a single loudspeaker. The compensation strategy exploits the part of the growth function of the loudspeaker distortion which is almost linear, and thus suppresses the distortion it generates while retaining a larger portion of DPOAE in the residual signal. The cancellation strategy utilizes a one-dimensional Volterra filter to remove the cubic distortion from the loudspeaker. Testing on normal-hearing ears shows that the compensation strategy improved the DPOAE-to-interference ratio by approximately 7 dB, resulting in a cross-correlation of 0.62 between the residual DPOAE level and the true DPOAE level. Meanwhile, the cancellation strategy directly recovered both the magnitude and the phase of DPOAE, reducing the magnitude estimation error from 15.5 dB to 3.9 dB in the mean-square sense. These pilot results suggest that the cancellation strategy may be suitable for further testing with more subjects.
畸变产物耳声发射（DPOAE）是在耳蜗内波放大过程中产生的向后传播的波。DPOAE信号可以在相对嘈杂的条件下快速检测到。近年来，耳机行业对采用DPOAE作为附加功能以使他们的产品能够“智能”了解内耳状态表现出兴趣。然而，一个技术挑战仍有待解决——耳机中的扬声器会在与DPOAE相同的频率上产生自身的三次谐波失真。不幸的是，扬声器失真的强度通常与DPOAE的强度相当，甚至可能更高。在本研究中，我们提出了两种策略，即补偿策略和抵消策略，以实现用单个扬声器进行DPOAE测量。补偿策略利用扬声器失真增长函数中几乎呈线性的部分，从而抑制其产生的失真，同时在残余信号中保留较大比例的DPOAE。抵消策略利用一维沃尔泰拉滤波器去除扬声器的三次谐波失真。对正常听力耳朵的测试表明，补偿策略使DPOAE与干扰的比率提高了约7 dB，残余DPOAE水平与真实DPOAE水平之间的互相关系数为0.62。同时，抵消策略直接恢复了DPOAE的幅度和相位，在均方意义上，幅度估计误差从15.5 dB降低到3.9 dB。这些初步结果表明，抵消策略可能适合对更多受试者进行进一步测试。
