Weatherproofing or ingress protection (IP) is an important reliability requirement for microphone designs. The most common microphone weatherproofing approach is to cover the acoustic porthole with an acoustically transparent mesh layer. This approach is usually effective to protect the microphone from typical dust and water damages but may not prevent the microphone performance such as frequency response (FR) from shifting away from the default behavior. For microphones used in external environments, especially the exterior of a vehicle, there are higher risks of FR characteristics shifting due to foreign object contaminations. Changes in FR characteristics often degrade the performance of microphone dependent applications or even prevent them from functioning completely. To understand how FR could change when being contaminated, microphone samples of three design types are tested under contamination conditions possibly encountered during vehicle operations, including water and moisture, dry sand and dust, and wet mud. The three microphone types come with different weatherproof design features, such as treating the porthole with acoustic meshes or structurally sealing the entire housing. It is shown that, among different contamination conditions considered in this study, dry dust/sand presents minimal influences on microphone responses, followed by water/moisture, then wet mud causing the most significant impact. Furthermore, it is also demonstrated that, for non-sealed microphones regardless how the porthole is protected with mesh layers, there is always a chance for foreign objects (e.g., water, dust, mud) to migrate into the microphone thus significantly change the microphone performance.
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