Valerie Rennoll will present her research proposal entitled, “Acoustic impedance-matched sensor developed towards wearable body sound monitoring” on Thursday, April 28 at 3pm via Zoom. https://wse.zoom.us/j/96746949427
Abstract:
Acoustic sensors detect mechanical vibrations in solid, liquid, and gas media with a wide variety of applications including, but not limited to, body sound monitoring, underwater navigation, and material defect inspection. Current sensors designed to capture sound in the audible frequency range, such as microphones and accelerometers, generally have an acoustic impedance that significantly differs from the medium being probed. This acoustic impedance mismatch results in a significant amount of signal energy being reflected at the boundary between the medium and sensor. When microphones are used to capture sound from various media, airborne noise can also easily corrupt the signal of interest, which often has a low amplitude.
The proposed work focuses on constructing an impedance-matched acoustic sensor that implements noise rejection with a physics-based approach and uses flexible materials. The sensor is used to capture sound from the body, musical instruments, and underwater, and then specifically optimized for long-term monitoring of respiratory and cardiac sounds.
When the diaphragm matches the acoustic impedance of skin, the sensor is shown to capture respiratory sounds with minimal interference from airborne noise at sound levels up to 85 dB.
While researchers have developed various solutions for body sound monitoring, two challenges that remain are how to objectively compare the characteristics of multiple devices and mitigate the perceived differences in sound quality. To address these challenges, an acoustic phantom is developed to excite and compare the acoustical characteristics of multiple devices without coloration from the phantom itself via a whitening procedure. A general equalization method is also presented that alters the perceptual characteristics of a device and was specifically shown to increase the perceived similarity between electronic and acoustic stethoscopes. Overall, the combined approach to sound pickup through materials study, sensor design, and processing methods is expected to deliver a device with high sensitivity through impedance matching that can improve respiratory and cardiac monitoring.
