Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zürich, University of Zürich, Rämistrasse 100, 8091 Zürich, Switzerland.
Department of Mechanical Engineering, Incheon National University, 119 Academy-ro, Songdo 1(il)-dong, Yeonsu-gu, Incheon, Republic of Korea.
J Acoust Soc Am. 2022 Mar;151(3):1593. doi: 10.1121/10.0009676.
This study is aimed at the quantitative investigation of wave propagation through the skull bone and its dependence on different coupling methods of the bone conduction hearing aid (BCHA). Experiments were conducted on five Thiel embalmed whole head cadaver specimens. An electromagnetic actuator from a commercial BCHA was mounted on a 5-Newton steel headband, at the mastoid, on a percutaneously implanted screw (Baha Connect), and transcutaneously with a Baha Attract (Cochlear Limited, Sydney, Australia), at the clinical bone anchored hearing aid (BAHA) location. Surface motion was quantified by sequentially measuring ∼200 points on the skull surface via a three-dimensional laser Doppler vibrometer (3D LDV) system. The experimental procedure was repeated virtually, using a modified LiUHead finite element model (FEM). Both experiential and FEM methods showed an onset of deformations; first near the stimulation area, at 250-500 Hz, which then extended to the inferior ipsilateral skull surface, at 0.5-2 kHz, and spread across the whole skull above 3-4 kHz. Overall, stiffer coupling (Connect versus Headband), applied at a location with lower mechanical stiffness (the BAHA location versus mastoid), led to a faster transition and lower transition frequency to local deformations and wave motion. This behaviour was more evident at the BAHA location, as the mastoid was more agnostic to coupling condition.
本研究旨在定量研究颅骨中的波传播及其对骨导助听器（BCHA）不同耦合方法的依赖性。实验在五个经泰尔氏液防腐处理的全头颅尸体标本上进行。商业 BCHA 的电磁驱动器安装在 5 牛顿钢头带、经皮植入的螺钉（Baha Connect）和经皮的 Baha Attract（澳大利亚悉尼 Cochlear Limited）上，位置在临床骨锚定听力植入（BAHA）处。通过三维激光多普勒测振仪（3D LDV）系统，逐点测量颅骨表面约 200 个点，以定量测量表面运动。使用改进的 LiUHead 有限元模型（FEM），在虚拟环境中重复了实验过程。实验和 FEM 方法都显示出变形的起始；首先在刺激区域附近，在 250-500 Hz 时，然后延伸到同侧颅骨表面的下方，在 0.5-2 kHz 时，在 3-4 kHz 以上传播到整个颅骨。总体而言，在机械刚度较低的位置（BAHA 位置相对于乳突）施加更刚性的耦合（Connect 与 Headband）会导致更快的过渡和更低的过渡频率到局部变形和波运动。这种行为在 BAHA 位置更为明显，因为乳突对耦合条件的敏感性较低。
