FINITE ELEMENT SIMULATION OF SOUND WAVE PROPAGATION INTO THE HUMAN HEAD

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 空军科学研究办公室（AFOSR）对寻找声能进入人类头部的途径感兴趣。由于在航空母舰的飞行甲板上遇到的高声级，即使戴着耳塞和耳罩也可能遭受听力损失。这是由于声音通过传导路径而不是空气到达耳蜗。这项研究的目标是找到这些通路，以便开发设备来减少通过它们传播的声能。为了验证这些路径，有必要获得整个头部的压力。由于我们有兴趣在高水平声音的情况下学习耳朵的路径，因此必须进行模拟。头部是具有多层和复杂几何形状的复杂散射体，因此不存在封闭形式的解。离散时间有限元方法允许模拟具有多层的复杂几何形状，因此非常适合近似来自人类头部的声音散射。可以用来近似能量传播的方法是声线追踪。射线追踪使用从有限元代码计算的压力数据来传播通过几何形状的射线网格，当几何声学是适当的时，该几何形状应当大致对应于由几何声学预测的射线路径。然后，我们可以通过沿传播方向穿过横截面的射线的密度来近似计算体积中的能量。通过这种方式，可以通过定位具有高密度射线穿过的路径来确定主导能量路径。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Air Force Office of Scientific Research (AFOSR) is interested in finding the pathways through which sound energy travels into the human head. Due to the high sound levels encountered on the flight deck of air craft carriers, it is possible to suffer hearing loss even when wearing ear plugs and ear muffs. This is due to sound reaching the cochlea through conducting pathways other than air. The goal of this research is to find these pathways so that devices may be developed to reduce the acoustic energy traveling through them. In order to verify these paths it is necessary to obtain the pressure throughout the head. Since we are interested in learning the pathways to the ear in situations with high levels of sound, a simulation must be performed. The head is a complex scatterer with multiple layers and complex geometries so a closed form solution doesn't exist. The discrete-time finite element method allows for simulation of complex geometries with multiple layers, and is therefore ideal for approximating sound scattering from the human head. A method that can be used to approximate the propagation of energy is acoustic ray tracing. Ray tracing uses the pressure data computed from the finite element code to propagate a grid of rays through the geometry that should roughly correspond to the ray paths predicted by geometrical acoustics when geometrical acoustics are appropriate. One can then approximate the energy in a volume by the density of rays going through a cross-section in the direction of propagation. In this way, one can determine the dominant energy pathways by locating the paths with a high density of rays passing through it.