Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
Department of Mathematics and Department of Statistical Science, Duke University, Durham, North Carolina 27708, USA.
J Acoust Soc Am. 2021 Apr;149(4):2659. doi: 10.1121/10.0004264.
Click-evoked otoacoustic emissions (CEOAEs) are clinically used as an objective way to infer whether cochlear functions are normal. However, because the sound pressure level of CEOAEs is typically much lower than the background noise, it usually takes hundreds, if not thousands, of repetitions to estimate the signal with sufficient accuracy. In this paper, we propose to improve the signal-to-noise ratio (SNR) of CEOAE signals within limited measurement time by optimal shrinkage (OS) in two different settings: covariance-based optimal shrinkage (cOS) and singular value decomposition-based optimal shrinkage (sOS). By simulation, the cOS consistently enhanced the SNR by 1-2 dB from a baseline method that is based on calculating the median. In real data, however, the cOS cannot enhance the SNR over 1 dB. The sOS achieved a SNR enhancement of 2-3 dB in simulation and demonstrated capability to enhance the SNR in real recordings. In addition, the level of enhancement increases as the baseline SNR decreases. An appealing property of OS is that it produces an estimate of all single trials. This property makes it possible to investigate CEOAE dynamics across a longer period of time when the cochlear conditions are not strictly stationary.
Click-evoked 耳声发射（CEOAEs）被临床用作推断耳蜗功能是否正常的一种客观方法。然而，由于 CEOAE 的声压级通常比背景噪声低得多，因此通常需要数百次甚至数千次重复才能以足够的精度估计信号。在本文中，我们提出了两种不同设置下通过最优收缩（OS）来提高 CEOAE 信号的信噪比（SNR）的方法：基于协方差的最优收缩（cOS）和基于奇异值分解的最优收缩（sOS）。通过模拟，cOS 始终将基于计算中位数的基线方法的 SNR 提高了 1-2 dB。然而，在实际数据中，cOS 无法将 SNR 提高超过 1 dB。sOS 在模拟中实现了 2-3 dB 的 SNR 增强，并证明了在实际记录中增强 SNR 的能力。此外，增强水平随着基线 SNR 的降低而增加。OS 的一个吸引人的特性是它可以对所有单次试验进行估计。当耳蜗条件不是严格稳定时，该特性使得有可能在更长的时间段内研究 CEOAE 动态。
