Optimized Acoustic Phantom Design for Characterizing Body Sound Sensors

Abstract

Many commercial and prototype devices are available for capturing body sounds that provide important information on the health of the lungs and heart; however, a standardized method to characterize and compare these devices is not agreed upon. Acoustic phantoms are commonly used because they generate repeatable sounds that couple to devices using a material layer that mimics the characteristics of skin. While multiple acoustic phantoms have been presented in literature, it is unclear how design elements, such as the driver type and coupling layer, impact the acoustical characteristics of the phantom and, therefore, the device being measured. Here, a design of experiments approach is used to compare the frequency responses of various phantom constructions. An acoustic phantom that uses a loudspeaker to generate sound and excite a gelatin layer supported by a grid is determined to have a flatter and more uniform frequency response than other possible designs with a sound exciter and plate support. When measured on an optimal acoustic phantom, three devices are shown to have more consistent measurements with added weight and differing positions compared to a non-optimal phantom. Overall, the statistical models developed here provide greater insight into acoustic phantom design for improved device characterization.

Electrostatic Acoustic Sensor with an Impedance-Matched Diaphragm Characterized for Body Sound Monitoring

“…To demonstrate this effect with acoustic impedance-matched polymers fabricated for the AIMS, an acoustic phantom previously presented by the authors was modified so that materials, such as wood and plastic, could be excited in place of a gelatin layer. The modified phantom, shown in Figure , contains a loudspeaker that excites a base material supported by a heavy aluminum plate and held fixed with magnets.…”

“…To measure the frequency response in conditions more similar to body sound monitoring and to compare to existing stethoscopes, the AIMS was placed at the center of an acoustic phantom, held with a 200 g weight, and excited with a logarithmically swept sine sweep, as previously described by the authors . As a summary, room EQ wizard (REW) software generated a sine sweep and analyzed the response of the AIMS using the methods outlined by Müller .…”

Exploring Microphone Technologies for Digital Auscultation Devices

“…In this context, the intent of this work is to present a technology comparison, including MEMS solutions. Auscultation device testing is still in its infancy, and no standard is available [29], yet a possible approach consists of using phantoms that are either aircoupled [30] or gel-based [31]. In this work, we adopted a solution similar to the one proposed in [32], based on a water-filled polymer ball.…”