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Sound Attenuation Study of Micro-Scale Acoustic Package

Certain microelectromechanical systems (MEMS), particularly MEMS gyroscopes, are notably susceptible to high power acoustic noise, especially when the noise is at or near its resonant frequency. A micro scale open-through dual expansion chamber (ODEC) array package with a continuous transmission loss (TL) in a wide frequency range is proposed to diminish the impact of such noise on the performance of MEMS gyroscopes. An analytical model based on planar wave propagation in stationary air has been developed with the consideration of the thermo-acoustic effect near the inner rigid boundary regarding small scale. Experiments with ODEC groups and control groups (non-ODEC) samples have been conducted to verify the model and compare the performances. The ODECs perform in the manner of low-pass filters and both the experimental and the analytical results exhibit greater TL in the higher frequency ranges as compared to the corresponding control samples. In addition, the resonance effects of the ODEC itself are also experimentally observed to be a key factor in influencing the TL.