SNR enhancement of a spin-MEMS microphone by optimum bias magnetic field and demonstration of operation sound monitoring of rotating equipment

We report on a wide-bandwidth Spin-MEMS microphone, in which spintronic strain-gauge sensors (Spin-SGSs) based on magnetic tunnel junctions are integrated on a diaphragm, with a mechanical resonance frequency of over 70 kHz and a signal-to-noise ratio (SNR) of 49 dB A. SNR enhancement is realized by adopting an optimum bias magnetic field. We compare operation sounds of defective and normal bearings using the packaged microphone. The Spin-MEMS microphone detects differences in the operation sounds between the defective and normal bearings at the high-frequency range of 10 kHz to 50 kHz, which is a promising result for fault prediction of rotating equipment.