Frequency lowering is a form of signal processing designed to deliver high-frequency speech cues to the residual hearing region of a listener with a high-frequency hearing loss. While this processing technique has been shown to improve the intelligibility of fricative and affricate consonants, perception of place of articulation has remained a challenge for hearing-impaired listeners, especially when the bandwidth of the speech signal is reduced during the frequency-lowering processing. This paper describes a modified vocoder-based frequency-lowering system similar to one reported by Posen et al. (1993), with the goal of improving place-of-articulation perception by enhancing the spectral differences of fricative consonants. In this system, frequency lowering is conditional; it suppresses the processing whenever the high-frequency portion (>400 Hz) of the speech signal is a periodic signal. In addition, the system separates non-sonorant consonants into three classes based on the spectral information (slope and peak location) of fricative consonants. Results from a group of normal-hearing listeners with our modified system show improved perception of frication and affrication features, as well as place-of-articulation distinction, without degrading the perception of nasals and semivowels compared to low-pass filtering and Posen et al.’s system.

降频是一种信号处理形式，旨在将高频语音提示传递到具有高频听力损失的听众的残余听力区域。虽然这种处理技术已被证明可以提高擦音和塞擦辅音的可懂度，但发音位置的感知对于听力受损的听众来说仍然是一个挑战，特别是当语音信号的带宽在降频处理期间减少时。本文描述了一种改进的基于声码器的降频系统，类似于 Posen 等人报道的系统。(1993)，目的是通过增强摩擦辅音的频谱差异来改善发音位置的感知。在这个系统中，频率降低是有条件的；每当高频部分 (> 400 Hz) 的语音信号是一个周期信号。此外，系统根据摩擦辅音的频谱信息（斜率和峰值位置）将非辅音辅音分为三类。与低通滤波和 Posen 等人相比，使用我们改进系统的一组听力正常的听众的结果显示，对摩擦和摩擦特征的感知以及发音部位的区别有所改善，而不会降低对鼻音和半元音的感知.的系统。