Department of Speech, Language, and Hearing Sciences, University of Colorado Boulder, Boulder, Colorado 80309, USA.
Ear Hear. 2013 May-Jun;34(3):251-60. doi: 10.1097/AUD.0b013e318271aa5e.
Hearing aids use complex processing intended to improve speech recognition. Although many listeners benefit from such processing, it can also introduce distortion that offsets or cancels intended benefits for some individuals. The purpose of the present study was to determine the effects of cognitive ability (working memory) on individual listeners' responses to distortion caused by frequency compression applied to noisy speech.
The present study analyzed a large data set of intelligibility scores for frequency-compressed speech presented in quiet and at a range of signal-to-babble ratios. The intelligibility data set was based on scores from 26 adults with hearing loss with ages ranging from 62 to 92 years. The listeners were grouped based on working memory ability. The amount of signal modification (distortion) caused by frequency compression and noise was measured using a sound quality metric. Analysis of variance and hierarchical linear modeling were used to identify meaningful differences between subject groups as a function of signal distortion caused by frequency compression and noise.
Working memory was a significant factor in listeners' intelligibility of sentences presented in babble noise and processed with frequency compression based on sinusoidal modeling. At maximum signal modification (caused by both frequency compression and babble noise), the factor of working memory (when controlling for age and hearing loss) accounted for 29.3% of the variance in intelligibility scores. Combining working memory, age, and hearing loss accounted for a total of 47.5% of the variability in intelligibility scores. Furthermore, as the total amount of signal distortion increased, listeners with higher working memory performed better on the intelligibility task than listeners with lower working memory did.
Working memory is a significant factor in listeners' responses to total signal distortion caused by cumulative effects of babble noise and frequency compression implemented with sinusoidal modeling. These results, together with other studies focused on wide-dynamic range compression, suggest that older listeners with hearing loss and poor working memory are more susceptible to distortions caused by at least some types of hearing aid signal-processing algorithms and by noise, and that this increased susceptibility should be considered in the hearing aid fitting process.
助听器采用复杂的处理技术来提高言语识别能力。尽管许多听众受益于这种处理，但它也会引入失真，从而抵消或取消一些个体的预期收益。本研究的目的是确定认知能力（工作记忆）对个体听众对噪声语音频率压缩引起的失真的反应的影响。
本研究分析了大量在安静和各种信噪比下呈现的频率压缩语音的可懂度得分数据集。该可懂度数据集基于 26 名年龄在 62 至 92 岁之间的听力损失成年人的得分。根据工作记忆能力将听众分组。使用音质度量来测量频率压缩和噪声引起的信号修改（失真）量。使用方差分析和层次线性建模来识别由于频率压缩和噪声引起的信号失真，各组受试者之间的有意义差异。
工作记忆是影响在噪声语音中呈现的句子以及基于正弦模型进行频率压缩的句子的可懂度的重要因素。在最大信号修改（由频率压缩和噪声引起）的情况下，工作记忆（在控制年龄和听力损失的情况下）因素占可懂度得分方差的 29.3%。将工作记忆、年龄和听力损失结合起来，可解释可懂度得分变异性的 47.5%。此外，随着信号失真总量的增加，工作记忆较高的听众在可懂度任务中的表现优于工作记忆较低的听众。
工作记忆是听众对由噪声和正弦模型实现的频率压缩的累积效应引起的总信号失真的反应的重要因素。这些结果与其他专注于宽动态范围压缩的研究一起表明，听力损失和工作记忆较差的老年听众更容易受到至少某些类型的助听器信号处理算法和噪声引起的失真的影响，并且在助听器适配过程中应考虑到这种增加的易感性。
