Moore B C, Glasberg B R, Vickers D A
Department of Experimental Psychology, University of Cambridge.
Br J Audiol. 1995 Jun;29(3):131-43. doi: 10.3109/03005369509086590.
This experiment simulated the threshold elevation and loudness recruitment associated with three different types of hearing loss: moderate flat (condition R2), severe flat (condition R3), and moderate-to-severe sloping (condition RX). This was done to allow an examination of the effects of these factors on the intelligibility of speech, in isolation from other factors that are normally associated with cochlear hearing loss, such as reduced frequency selectivity. The speech was presented at a fixed input level of 65 dB SPL, against a background of a noise whose spectrum was shaped to match the long-term average spectrum of the speech. The level of the background noise varied from 65 to 74 dB SPL. The simulation was performed by splitting the input signal into 13 frequency bands, and processing the envelope in each band so as to create loudness sensations in a normal ear that would resemble those produced in an impaired ear with recruitment. The bands were then recombined. All tests were performed using subjects with normal hearing. The simulation of hearing loss produced decrements in performance. The speech in condition R3 was inaudible. For conditions R2 and RX, the speech-to-noise ratios had to be up to 6 dB higher than in the control condition (R1, unprocessed stimuli) to achieve similar levels of performance. When linear amplification according to the NAL prescription was applied before the simulation, performance improved markedly for conditions R2 and RX, and did not differ significantly from that for R1. For condition R3, performance with simulated NAL amplification remained below that for condition R1; the decrement in performance was equivalent to about a 1 dB change in speech-to-noise ratio. The results of the present experiment show much smaller decrements in performance than those of an earlier experiment using a single talker as the interfering sound (Moore and Glasberg, 1993). It appears that loudness recruitment and threshold elevation have larger effects for a fluctuating background sound than for a steady background sound, and linear amplification is more effective in the latter case.
中度平坦型（R2条件）、重度平坦型（R3条件）和中度至重度斜坡型（RX条件）。这样做是为了能够单独研究这些因素对言语可懂度的影响，而不受通常与耳蜗性听力损失相关的其他因素（如频率选择性降低）的干扰。言语以65 dB SPL的固定输入水平呈现，背景噪声的频谱经过调整，以匹配言语的长期平均频谱。背景噪声水平在65至74 dB SPL之间变化。模拟过程是将输入信号分成13个频段，对每个频段的包络进行处理，以便在正常耳朵中产生类似于在有重振的受损耳朵中产生的响度感觉。然后将这些频段重新组合。所有测试均使用听力正常的受试者进行。听力损失的模拟导致了性能下降。R3条件下的言语听不见。对于R2和RX条件，言语噪声比必须比对照条件（R1，未处理的刺激）高6 dB才能达到相似的性能水平。在模拟之前应用根据NAL处方的线性放大时，R2和RX条件下的性能显著改善，与R1条件下的性能没有显著差异。对于R3条件，模拟NAL放大后的性能仍低于R1条件；性能下降相当于言语噪声比约1 dB的变化。本实验的结果显示，与早期使用单个说话者作为干扰声音的实验（Moore和Glasberg，1993）相比，性能下降要小得多。似乎响度重振和阈值升高对波动背景声音的影响比对稳定背景声音的影响更大，并且线性放大在后者情况下更有效。
