Evaluation of sensing properties of stiffness-sensitive electret microphones

This paper presents an evaluation of the sensing properties of a new thin-film stiffness sensing technology that utilizes commercial electret microphones. The analysis is intended to provide researchers with both quantitative and qualitative information on microphone selection for stiffness sensing applications. The sensing properties examined include sensitivity, selectivity and the effect of microphoneʹs electric field. Specifically, a mathematical method to estimate the stiffness sensitivity of a commercial microphone from its acoustic sensitivity is presented. This method utilizes direct measurements of the microphoneʹs parameters to compute sensitivity to thin-film stiffness changes. The discussion on selectivity focuses on undesired cross-stiffness changes in the microphone membrane in the presence of changes in unrelated environmental analytes. Finally, the influence of the microphoneʹs electric field on its stiffness sensing ability is presented.