Microphone for a listening device having a reduced humidity coefficient

摘要

A microphone is constructed to be more tolerant to a wide range of relative humidity conditions without adversely affecting the performance of the microphone. The microphone includes a housing with a sound port for receiving sound and an electret assembly for converting the sound into an output signal. The electret assembly includes a diaphragm and a backplate. The backplate is made of at least two layers, usually polymeric layers. The first layer of material has a first hygroscopic coefficient and a second layer of material has a second hygroscopic coefficient. The first and second layers cause the backplate to bend in response to higher humidity conditions, thereby minimizing the adverse effects on microphone performance caused by characteristic changes in the diaphragm at the higher humidity conditions.