Design Of Double-membrane T-type MEMS Electronic Stethoscope

Based on the MEMS vector hydrophone,the MEMS electronic stethoscope developed by North University of China also shows good performance in the field of heart sound detection,such as high sensitivity,high signal-to-noise ratio,low cost,mass processing and other advantages.The main work of this paper has two points: the first is to improve the packaging and structure of the sensor to improve the sensitivity and signal-to-noise ratio of the sensor;the second is to test a large number of heart sound signals to verify the feasibility of MEMS electronic stethoscope,and finally the detection of the patient's heart sound signals laid the foundation for the future application in the medical field.Heart disease and cardiovascular disease have become the number one killer threatening the safety and health of human life.Nowadays,the detection of human heart mostly includes ECG detection,coronary angiography and traditional auscultation.However,the lag of ECG,the high cost of coronary angiography,the subjective assumption of invasive detection and traditional auscultation of heart sound will affect the detection of patients' heart.Auscultation of heart sounds is the oldest and most common method of heart detection,which can be traced back to the 19 th century and has been used up to now.And the detection of heart sound has been proved to have an early screening effect on cardiovascular disease in domestic and foreign studies.The MEMS electronic stethoscope designed in this paper mainly transforms the heart sound signal picked up by the sensor probe into electrical signal through signal processing technology,which makes the physical signal visible,and can analyze the characteristics of heart sound signal preliminarily from time domain and frequency domain,which greatly reduces the subjective assumption of doctors on the heart sound signal of patients.The application of MEMS electronic stethoscope in the medical field has also greatly reduced the medical cost of patients,and can play an early prevention and screening role.In the early stage,the single membrane sensor shell will absorb the acoustic signal,resulting in the low signal-to-noise ratio of the heart sound signal output by the sensor.In order to eliminate this kind of influence,the double film packaging structure is proposed in this paper.The packaging structure overlaps the original acoustic signal and the reflected acoustic signal,and improves the signal-to-noise ratio of the output signal.The feasibility of the packaging structure is verified by theoretical simulation analysis.The design optimization of the pick-up structure improves the sensitivity of the sensor,and plays an important role in the detection of the first and second heart sounds,as well as the time and frequency domain analysis of the heart sounds.Whether the sensor can have a good frequency response in the frequency band of clinical heart sound signal is the key factor in the design of sensor microstructure.The T-shaped microstructure designed in this paper is mainly verified by mechanical modeling and theoretical analysis,and the improvement of its structure is verified by later experimental verification and heart sound signal test,which also proves that the structure can meet the heart sound signal detection.Finally,the experimental results show that the sensitivity of the MEMS electronic stethoscope designed in this paper is-179db@500Hz,SNR is 38 dB,which meets the design requirements.