Ohlenforst Barbara, Souza Pamela E, MacDonald Ewen N
1Centre for Applied Hearing Research (CAHR), Technical University of Denmark (DTU), Lyngby, Denmark; and 2Communication Sciences and Disorders and Knowles Hearing Center Northwestern University, Evanston, Illinois, USA.
Ear Hear. 2016 Mar-Apr;37(2):137-43. doi: 10.1097/AUD.0000000000000240.
Previous work has shown that individuals with lower working memory demonstrate reduced intelligibility for speech processed with fast-acting compression amplification. This relationship has been noted in fluctuating noise, but the extent of noise modulation that must be present to elicit such an effect is unknown. This study expanded on previous study by exploring the effect of background noise modulations in relation to compression speed and working memory ability, using a range of signal to noise ratios.
Twenty-six older participants between ages 61 and 90 years were grouped by high or low working memory according to their performance on a reading span test. Speech intelligibility was measured for low-context sentences presented in background noise, where the noise varied in the extent of amplitude modulation. Simulated fast- or slow-acting compression amplification combined with individual frequency-gain shaping was applied to compensate for the individual's hearing loss.
Better speech intelligibility scores were observed for participants with high working memory when fast compression was applied than when slow compression was applied. The low working memory group behaved in the opposite way and performed better under slow compression compared with fast compression. There was also a significant effect of the extent of amplitude modulation in the background noise, such that the magnitude of the score difference (fast versus slow compression) depended on the number of talkers in the background noise. The presented signal to noise ratios were not a significant factor on the measured intelligibility performance.
In agreement with earlier research, high working memory allowed better speech intelligibility when fast compression was applied in modulated background noise. In the present experiment, that effect was present regardless of the extent of background noise modulation.
先前的研究表明，工作记忆能力较低的个体在使用快速作用的压缩放大处理语音时，可懂度会降低。这种关系在波动噪声中已被注意到，但引发这种效应所需的噪声调制程度尚不清楚。本研究通过使用一系列信噪比，探讨背景噪声调制与压缩速度和工作记忆能力之间的关系，对先前的研究进行了扩展。
根据26名年龄在61至90岁之间的老年参与者在阅读广度测试中的表现，将他们按工作记忆的高低分组。测量了在背景噪声中呈现的低语境句子的语音可懂度，其中噪声的幅度调制程度有所不同。应用模拟的快速或慢速作用的压缩放大结合个体频率增益整形来补偿个体的听力损失。
当应用快速压缩时，高工作记忆的参与者的语音可懂度得分比应用慢速压缩时更高。低工作记忆组的表现则相反，与快速压缩相比，在慢速压缩下表现更好。背景噪声中的幅度调制程度也有显著影响，使得得分差异（快速与慢速压缩）的大小取决于背景噪声中的说话者数量。呈现的信噪比不是影响测量的可懂度表现的显著因素。
与早期研究一致，在调制背景噪声中应用快速压缩时，高工作记忆能带来更好的语音可懂度。在本实验中，无论背景噪声调制程度如何，这种效应都存在。
