Active and passive stethoscope frequency transfer functions: Electronic stethoscope frequency response

Abstract

New low cost electronic stethoscopes are being developed to address telemedicine needs [6,7,8] and hospital acquired infections [4,5] that will require a means to effectively compare their acoustical performance. While the human ear may detect some qualitative differences between scopes the study here presents an experimental method that measures the step response of different electronic and passive stethoscopes, and then calculates their frequency transfer function so that they may be compared quantitatively. This study presents comparative results of passive stethoscopes (disposable and nurse types) with a commercially available electronic stethoscope (Littmann) and a new, very low cost, electronic stethoscope still in development for medical purposes [6]. This new design utilizes a commercially available cell phone for signal processing. Our results show that both passive and electronic types have resonant type responses resulting in poor low and high frequency transmission, but electronic amplification helps aid the stethoscope function in those extremes. We also show that the new, very low cost, electronic stethoscope design was found to have comparable performance and even better sensitivity to currently marketed electronic stethoscopes.