This paper describes the development of a frequency sensitive acoustic transducer that operates in the 10 Hz to 10 kHz regime. This device uses modern silicon microfabrication techniques to form mechanical times that resonate at specified frequencies. This high-sensitivity device is intended for low-power battery powered applications.
"LLNL's acoustic spectrometer", Proc. SPIE 3081, Peace and Wartime Applications and Technical Issues for Unattended Ground Sensors, (24 July 1997); doi: 10.1117/12.280641; https://doi.org/10.1117/12.280641