Design of a high SNR electronic heart sound sensor based on a MEMS bionic hydrophone

Haixia Li,Guojun Zhang,Yongfeng Ren,Qingda Xu,Lansheng Zhang,Sicun Duan,Jiangong Cui,Renxin Wang,Ting Zhang,Xiaoyong Zhang

doi:10.1063/1.5062619

Haixia Li, Guojun Zhang + Show 8 more

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https://doi.org/10.1063/1.5062619

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Abstract

Since most of the contact conduction type of heart sound sensors don’t take into account the acoustic signal attenuation problem caused by the heart sound signal transmitting to a sensor whose filling materials’ impedance is different to human soft tissue, the signal-to-noise ratio (SNR) of the heart sound sensors is not very well. Human heart is immersed in blood. If the sensor’s core sensitive element can be immersed in fluid, the attenuation of heart sound signal may be decreased greatly. Inspired by the principle of hydroacoustic signal’s detection, this paper proposes the design of heart sound sensor based on the bionic vector hydrophone. Then theoretical analysis and finite element method (FEM) simulation about the sensor have been carried out. Combined sensitivity with resonant frequency, the optimum dimension of the sensor’s structure has been determined. The sensor’s micro-structure has been fabricated by using Micro-Electro-Mechanical System (MEMS) technology and coupling encapsulated by choosing a kind of medical coupling agent as the filling material. Finally, the performance of the proposed sensor is tested. The fact is that the proposed sensor can work well with either healthy people or patients with heart disease. The obtained data clearly show that: the SNR of the proposed heart sound sensor is superior to 3200-type of 3M Littmann 8.2 dB.

Highlights

Heart sound signal is one of the most important acoustic signals of human body
Heart sound sensors of electronic stethoscopes can be divided into two types: air conduction type and contact conduction type
Its ability of anti-interference and sensitivity is much higher than the former.7–10. It does not take into account the signal attenuation problem caused by the heart sound signal transmitting to the sensor whose filling materials’ impedance is different to human soft tissue

Summary

Introduction

Heart sound signal is one of the most important acoustic signals of human body. The change of heart sound and the occurrence of murmurs tend to be the earliest signs of the organic heart disease. auscultation has been emphasized again to solve the early detection of cardiovascular disease. traditional stethoscope requires rich clinical experience and good listening skills. Heart sound sensors of electronic stethoscopes can be divided into two types: air conduction type and contact conduction type.. Heart sound sensors of electronic stethoscopes can be divided into two types: air conduction type and contact conduction type.6 The former mainly uses the electromagnetic coil or the electret capacity as the acoustic transducer. The former has low sensitivity and low SNR has good stability. Its ability of anti-interference and sensitivity is much higher than the former.7–10 It does not take into account the signal attenuation problem caused by the heart sound signal transmitting to the sensor whose filling materials’ impedance is different to human soft tissue. Piezoelectric sensors have significant electro-mechanical coupling scitation.org/journal/adv characteristics, the sensitivity of piezoelectric sensor is limited by the thickness of the piezoelectric vibrator because the piezoelectric can be damaged in use when it is made too thin.

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