Earplugs are used in various critical industrial sectors, such as construction, aviation, military and defense, transportation, and healthcare. However, they present inherent drawbacks, notably discomfort that can lead to inconsistent and incorrect use, thereby leaving a significant proportion of workers vulnerable to irreversible hearing damage, ranging from tinnitus to deafness. This discomfort is closely linked to a physical parameter known as static mechanical pressure (SMP), representing the pressure exerted by earplugs on the earcanal walls. Determining the SMP is crucial for developing earplugs that prioritize comfort. However, experimental studies in this area are scarce and there is no experimental set-up capable of measuring the SMP whether in vivo or ex vivo. The objective of this paper is to fill this gap by presenting a novel experimental system designed to mimic a real earcanal, equipped with an optical probe for precise pressure measurements at various points along the earcanal. This precision-targeted methodology holds the promise of yielding a comprehensive pressure map spanning the entirety of the contact area between the earplug and earcanal, thereby offering unprecedented insights into SMP distribution. To validate our test bench, we conducted experiments using cylindrical rolled-down PVC earplugs inserted into a rigid cylindrical earcanal replica of varying radii. We compared our results with data obtained from a commercially available radial force tester commonly used in investigating stent grafts. Once validation was achieved, we expanded our investigation to measure SMP across various types of earplugs. Additionally, we designed and measured the SMP using roll-down foam earplugs in an artificial earcanal shaped to resemble the human anatomy. Our experimental findings were corroborated with data from finite element method (FEM) numerical calculations. Apart from providing the first comprehensive characterization of the static mechanical pressure exerted by earplugs, our research reveals that with roll-down foam earplugs, increased compression prior to insertion leads to reduced SMP. The versatility of our specially designed test bench allows for mapping SMP caused by earplugs across diverse earcanal shapes. Integration of this instrument into design frameworks holds promise for enhancing the physical comfort of earplugs and, consequently, improving their overall efficacy in hearing protection.

中文翻译：

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耳塞局部静态机械压力的测量


耳塞用于各种关键工业领域，例如建筑、航空、军事和国防、交通和医疗保健。然而，它们存在固有的缺点，特别是不适，可能导致不一致和不正确的使用，从而使很大一部分工人容易遭受不可逆转的听力损伤，从耳鸣到耳聋。这种不适与称为静态机械压力 (SMP) 的物理参数密切相关，该参数代表耳塞对耳道壁施加的压力。确定 SMP 对于开发优先考虑舒适度的耳塞至关重要。然而，该领域的实验研究很少，并且没有能够测量体内或离体 SMP 的实验装置。本文的目的是通过提出一种新颖的实验系统来填补这一空白，该系统旨在模拟真实的耳道，并配备光学探头，可在耳道上的各个点进行精确的压力测量。这种精确定位的方法有望生成涵盖耳塞和耳道之间整个接触区域的全面压力图，从而为 SMP 分布提供前所未有的见解。为了验证我们的测试台，我们使用圆柱形卷起的 PVC 耳塞插入不同半径的刚性圆柱形耳道复制品中进行了实验。我们将我们的结果与从常用于研究支架移植物的市售径向力测试仪获得的数据进行了比较。验证完成后，我们扩大了调查范围，测量各种类型耳塞的 SMP。此外，我们还使用形状类似于人体解剖学的人工耳道中的卷下泡沫耳塞来设计和测量 SMP。 我们的实验结果得到了有限元法 (FEM) 数值计算数据的证实。除了首次全面表征耳塞施加的静态机械压力外，我们的研究还表明，对于卷下式泡沫耳塞，插入前增加压缩会导致 SMP 降低。我们专门设计的测试台具有多功能性，可以在不同的耳道形状上映射耳塞引起的 SMP。将该仪器集成到设计框架中有望增强耳塞的物理舒适度，从而提高其听力保护的整体功效。