Identification of human pulse waveform by silicon microphone chip

An Electret Condenser Microphone (ECM) fabricated by Micro Electro Mechanical System (MEMS) technology, or a silicon microphone, was employed as a novel apparatus for human pulse wave measurement. Since ECM frequency response characteristic, i.e. sensitivity, theoretically constant in the level at lower than resonance frequency as stiffness control, the slightest pressure difference at around 1.0Hz generated by human pulse waveform is expected to measure by this silicon microphone. However, with regard to MEMS-ECM as a single device, the difficulty arises in a possible sensitivity reduction due to a high input-impedance amplifier embedded in MEMS-ECM. We then determined the frequency response at around 1.0Hz, and based on this result we defined the compensation circuit by which the human pulse waveform was successfully obtained.