Moore B C, Glasberg B R
Department of Experimental Psychology, University of Cambridge, England.
J Acoust Soc Am. 1993 Oct;94(4):2050-62. doi: 10.1121/1.407478.
These experiments simulated the threshold elevation and loudness recruitment associated with three different types of cochlear 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 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. For speech in quiet, simulation of hearing loss produced a reduction in the ability to understand low-level speech. However, speech at sufficiently high levels was highly intelligible in all conditions. Linear amplification according to the National Acoustic Laboratory (NAL) prescription gave high intelligibility for speech at normal conversational levels. For speech presented at a fixed input level of 65 dB SPL, against a background of a single competing talker, simulation of hearing loss produced substantial decrements in performance. The speech-to-background ratios in conditions R2 and RX had to be 11-13 dB higher than in the control condition (unprocessed stimuli) to achieve similar levels of performance. Linear amplification according to the NAL prescription improved performance markedly for the conditions simulating flat losses, but was less effective for the condition simulating a sloping loss. This indicates that threshold elevation combined with recruitment produces a loss of intelligibility for speech in the presence of a single competing talker that is only partly compensated by linear amplification of the type typically used in hearing aids.
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）的影响。模拟是通过将输入信号分成13个频带，并处理每个频带中的包络，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来进行的。然后将这些频带重新组合。所有测试均使用听力正常的受试者进行。对于安静环境中的言语，模拟听力损失会导致理解低水平言语的能力下降。然而，在足够高的水平下，言语在所有条件下都具有很高的可懂度。根据国家声学实验室（NAL）处方进行的线性放大，使正常对话水平的言语具有很高的可懂度。对于在65 dB SPL的固定输入水平下呈现的言语，在有一个竞争说话者的背景下，模拟听力损失会导致表现大幅下降。R2和RX条件下的言语与背景比率必须比对照条件（未处理的刺激）高11 - 13 dB才能达到相似的表现水平。根据NAL处方进行的线性放大在模拟平坦型损失的条件下显著提高了表现，但在模拟斜坡型损失的条件下效果较差。这表明，在有一个竞争说话者的情况下，阈值升高与响度重振相结合会导致言语可懂度下降，而这种下降只能通过助听器中通常使用的那种线性放大得到部分补偿。
