Design, fabrication, and characterization of an electronic stethoscope based on piezoelectric micromachined ultrasonic transducer array

Traditional mechanical stethoscope has difficulty in capturing weak acoustic signals. In order to realize continuous and real-time monitoring of cardiovascular and pulmonary diseases, an electronic stethoscope based on piezoelectric micromachined ultrasonic transducer (PMUT) array is designed. The PMUT sensing unit employs a honeycomb structural design and arrangement, which not only achieves a high fill factor but also enhances the acoustic sensitivity of the PMUT array, enabling continuous monitoring of mechanical heart sound signals. The manufactured electronic stethoscope integrates the PMUT array with a regulating circuit, and is encapsulated by polyurethane material with acoustic impedance similar to that of human tissue, so as to obtain broadband machine acoustic physiological signals. The electronic stethoscope is characterized, and the results show that it has a sound pressure sensitivity of −167 dB (reference: 1 V/μPa) and noise resolution of 45 dB (reference: 1 μPa/√Hz). Test results confirm that the electronic stethoscope with the PMUT array enables the continuous heart sound monitoring and effectively identifies the characteristic signals associated with heart abnormalities.