面向中频段听阈突变听力损失的非均匀滤波器组设计*

滤波器组是气传导助听器进行听觉补偿的重要功能模块。针对现有固定滤波器组对中频段听阈突变听损听力图的匹配效果欠佳问题，本文提出一种13子带非均匀滤波器组设计方案。不同于现有固定滤波器组，本文首先将全频段进行等比例三段划分，便于滤波器组在相应频段内进行听损补偿；然后在低频和高频段子带具有较高分布密度的前提下，适当增加中频段子带的分布密度，以提升中频段听损补偿效果；最后根据听力图的倍频特征点确定子带的中心频率，从而得到适配听力图的子带排布方案。此外，将频率响应掩蔽技术和奈奎斯特滤波器用于各子带的产生，进一步降低了滤波器组群延时和硬件复杂度。仿真分析表明，相比于现有16子带非均匀滤波器组，本文滤波器组对各类型中频段听阈突变听损听力图的平均匹配性能提升了48.4%，群延时降低了11.7%。因此，所设计滤波器组在面向补偿中频段听阈突变听损的气传导助听器中具有一定应用价值。

Design of non-uniform filter bank targeting hearing loss with auditory thresholds changing sharply in middle frequencies

The filter bank is an important functional module for the auditory compensation of air-conduction hearing aids. For the existing fixed filter bank, the matching performance is not good enough for audiograms whose auditory thresholds change sharply in middle frequencies. To address this problem, a 13-band non-uniform filter bank is proposed in this paper. Different from the existing fixed filter bank, the whole frequency range is divided into three equal regions firstly, which facilitates the filter bank to compensate for the hearing loss in the corresponding region. Then, to enhance the compensation effect for the hearing loss in middle frequencies, we appropriately increase the resolution of subbands of middle regions while keeping higher resolution of subbands of low and high regions. Finally, the center frequency of each subband is determined according to the octave of a standard audiogram and a subband distribution that is suitable for audiogram matching is obtained. In addition, subbands of the filter bank are produced with the help of frequency response masking technique and Nyquist filters, which further reduces the group delay and hardware complexity of the filter bank. Simulation analysis shows that, compared with the state-of-the-art 16-band non-uniform filter bank, the average matching performance for audiograms whose auditory thresholds changing sharply in middle frequencies of the proposed filter bank is improved by 48.4% and the group delay is reduced by 11.7%. Therefore, the proposed filter bank is valuable to air-conduction hearing aids that aim to compensate for the hearing loss with auditory thresholds changing sharply in middle frequencies.