École de Technologie Superieure (ETS), Montréal, QC, Canada.
Institut de Recherche Robert-Sauvé en Santé et en Sécurité du Travail (IRSST), Montréal, QC, Canada.
Sci Rep. 2022 Sep 12;12(1):15336. doi: 10.1038/s41598-022-19641-3.
Passive earplugs are used to prevent workers from noise-induced hearing loss. However, earplugs often induce an acoustic discomfort known as the occlusion effect. This phenomenon corresponds to an increased auditory perception of the bone-conducted part of physiological noises at low-frequency and is associated with the augmentation of the acoustic pressure in the occluded earcanal. In this work, we report a new concept of passive earplugs for mitigating the occlusion effect between 100 Hz and 1 kHz. The strategy consists in reducing the input impedance of the earplug seen from the earcanal by using quasi-perfect broadband absorbers derived from the field of meta-materials. The proposed "meta-earplug" is made of 4 critically coupled Helmholtz resonators arranged in parallel. Their geometry is optimized using an evolutionary algorithm associated with a theoretical model of the meta-earplug input impedance. The latter is validated against a finite-element approach and impedance sensor measurements. The meta-earplug is manufactured by 3D printing. Artificial test fixtures are used to assess the occlusion effect and the insertion loss. Results show that the meta-earplug induces an occlusion effect approximately 10 dB lower than foam and silicone earplugs while it provides an insertion loss similar to the silicone earplug up to 5 kHz.
被动耳塞用于防止工人因噪声导致听力损失。然而，耳塞通常会引起一种称为封闭效应的声学不适。这种现象对应于低频生理噪声骨导部分听觉感知的增加，并且与封闭耳道中声压的增加有关。在这项工作中，我们报告了一种用于减轻 100 Hz 至 1 kHz 之间封闭效应的新型被动耳塞概念。该策略包括使用源自超材料领域的准完美宽带吸收体来降低耳塞从耳道看的输入阻抗。所提出的“元耳塞”由 4 个并行排列的临界耦合亥姆霍兹共振器组成。它们的几何形状使用与元耳塞输入阻抗的理论模型相关联的进化算法进行优化。后者通过有限元方法和阻抗传感器测量进行验证。元耳塞通过 3D 打印制造。人工测试夹具用于评估封闭效应和插入损耗。结果表明，与泡沫和硅树脂耳塞相比，元耳塞引起的封闭效应大约低 10 dB，而在 5 kHz 之前，它提供的插入损耗与硅树脂耳塞相似。
