Carillo Kévin, Sgard Franck, Dazel Olivier, Doutres Olivier
Institut de recherche Robert-Sauvé en santé et en sécurité du travail, Montréal, Québec, Canada.
Laboratoire d'Acoustique de l'Université du Mans, UMR CNRS 6613, Institut d'Acoustique - Graduate School (IA-GS), Le Mans Université, Le Mans, France.
J Acoust Soc Am. 2023 Oct 1;154(4):2099-2111. doi: 10.1121/10.0021185.
The use of passive earplugs is often associated with the occlusion effect: a phenomenon described as the increased auditory perception of one's own physiological noise at low frequencies. As a notable acoustic discomfort, the occlusion effect penalizes the use and the efficiency of earplugs. This phenomenon is objectively characterized by the increase in sound pressure level in the occluded ear canal compared to the open ear canal. Taking inspiration from acoustic metamaterials, a new design of a three-dimensional printed "meta-earplug," made of four Helmholtz resonators arranged in series, is proposed for achieving near zero objective occlusion effect measured on artificial ear in a broadband frequency range (300 Hz to 1 kHz). For this purpose, the geometry of the meta-earplug is optimized to achieve a null occlusion effect target based on an analytical model of the phenomenon. It results from the optimization process that the input impedance of the meta-earplug medial surface approximately matches the input impedance of the open ear canal, weighted by the ratio of volume velocity imposed by the ear canal wall to the ear canal cavity between open and occluded cases. Acoustic properties of the meta-earplug are also shown to significantly improve its sound attenuation at the piston-like mode of the system.
这是一种在低频下对自身生理噪声听觉感知增强的现象。作为一种明显的声学不适，堵塞效应不利于耳塞的使用和效率。这种现象的客观特征是与开放耳道相比，被堵塞耳道内声压级增加。借鉴声学超材料，提出了一种由四个串联排列的亥姆霍兹共振器制成的三维打印“超耳塞”新设计，目的是在宽带频率范围（300赫兹至1千赫）内，在人工耳上实现近乎零的客观堵塞效应测量值。为此，基于该现象的分析模型对超耳塞的几何形状进行优化，以实现零堵塞效应目标。优化过程的结果是，超耳塞内侧表面的输入阻抗大致与开放耳道的输入阻抗相匹配，该匹配由耳道壁施加的体积速度与开放和堵塞情况下耳道腔之间的比值加权。超耳塞的声学特性还表明，它能在系统的活塞式模式下显著提高其声衰减。
