Orf Martin, Hannemann Ronny, Obleser Jonas
Department of Psychology, University of Lübeck, Lübeck 23562, Germany
Center of Brain, Behavior and Metabolism (CBBM), University of Lübeck, Lübeck 23562, Germany.
J Neurosci. 2025 Mar 12;45(11):e0238242024. doi: 10.1523/JNEUROSCI.0238-24.2024.
Amplitude compression is an indispensable feature of contemporary audio production and especially relevant in modern hearing aids. The cortical fate of amplitude-compressed speech signals is not well studied, however, and may yield undesired side effects: We hypothesize that compressing the amplitude envelope of continuous speech reduces neural tracking. Yet, leveraging such a "compression side effect" on unwanted, distracting sounds could potentially support attentive listening if effectively reducing their neural tracking. In this study, we examined 24 young normal hearing (NH) individuals, 19 older hearing-impaired (HI) individuals, and 12 older normal hearing individuals. Participants were instructed to focus on one of two competing talkers while ignoring the other. Envelope compression (1:8 ratio, loudness-matched) was applied to one or both streams containing short speech repeats. Electroencephalography allowed us to quantify the cortical response function and degree of speech tracking. With compression applied to the attended target stream, HI participants showed reduced behavioral accuracy, and compressed speech yielded generally lowered metrics of neural tracking. Importantly, we found that compressing the ignored stream resulted in a stronger neural representation of the uncompressed target speech. Our results imply that intelligent compression algorithms, with variable compression ratios applied to separated sources, could help individuals with hearing loss suppress distraction in complex multitalker environments.
幅度压缩是当代音频制作中不可或缺的一项功能，在现代助听器中尤为重要。然而，对于经幅度压缩的语音信号在皮层中的变化情况，目前尚未得到充分研究，而且可能会产生不良副作用：我们推测，对连续语音的幅度包络进行压缩会降低神经跟踪能力。然而，如果能有效减少不需要的、分散注意力的声音的神经跟踪，利用这种针对此类声音的“压缩副作用”可能会有助于专注聆听。在本研究中，我们对24名年轻正常听力（NH）个体、19名老年听力受损（HI）个体和12名老年正常听力个体进行了测试。参与者被要求专注于两名相互竞争的讲话者中的一个，同时忽略另一个。对包含简短语音重复的一个或两个音流应用包络压缩（1:8比例，响度匹配）。脑电图使我们能够量化皮层反应功能和语音跟踪程度。当对被关注的目标音流应用压缩时，听力受损的参与者表现出行为准确性下降，并且经压缩的语音通常会使神经跟踪指标降低。重要的是，我们发现对被忽略的音流进行压缩会导致未压缩的目标语音在神经层面上有更强的表现。我们的研究结果表明，采用可变压缩比应用于不同声源的智能压缩算法，可能有助于听力损失患者在复杂的多讲话者环境中抑制干扰。
