Portable infrasound monitoring device with multiple MEMS pressure sensors

Microelectromechanical system (MEMS) sensors are mass-produced and are therefore expected to be available to produce low-cost devices for infrasound monitoring. A low-cost device is useful in constructing a sensor network with various scales of a few to numerous sensors. To test its feasibility, we developed a device consisting of 32 MEMS barometric pressure sensors. A laboratory experiment revealed that internal noise increases as a signal frequency increases, but the noise can be reduced by simple averaging. Based on this fact, we stacked eight MEMS barometric pressure sensors on a single board to assemble an infrasound monitoring device that enables detection of a signal with amplitude of more than approximately 5 Pa. A field test was conducted, deploying them in areas surrounding an active volcano, Sakurajima in Japan. Signals associated with explosive eruptions were observed clearly in the frequency region of 0.1–5 Hz. The source position was also estimated using signals obtained at four observation points. The estimated source position showed generally good agreement with that of the volcano crater. Results confirmed that signals around the acoustic cut-off frequency can be obtained by the device.