Design of MEMS microphone protective membranes for continuous outdoor applications

Abstract

Although most modern communication devices use of multiple MEMS-based microphones, their application in continuous-outdoor applications has so far been very limited. Specifically, for constant operation in humid, rainy environments, additional weather protection of the MEMS element is required. Thus, a protective 3D-printed membrane has been developed for a multichannel outdoor application to monitor noise emissions. The acoustic characteristics of the protection are assessed analytically, using simulations and experimentally in this paper. The vibrational modes are identified in the simulation, which can be used to implement practically usable membranes. The measurements performed are compared to simulation results. Deviations are explained based on different material parameters of the membrane, model assumptions and manufacturing processes. 3D-printed membranes have a different material structure which is more flexible than solid elements and need adapted simulations inputs. Running field tests show that the membranes developed can adequately protect MEMS-based microphones for several months with only a minor impact on the system’s acoustic performance. This paper proves that an adequate analytical, simulation and practical implementation is a cost effective and adaptable approach for outdoor noise monitoring systems.