Comparison of the characteristics of different types of acoustic sensors when recording respiratory noises on the surface of the human chest

Respiratory sounds recorded for diagnostic purposes on the surface of the chest lie in the frequency range from 70–80 to 1000 Hz. The problem is ensuring sufficient efficiency of mechanico-acoustical conversion and undistortedness of the amplitude-frequency and phase-frequency characteristics of contact acoustic sensors in the studied frequency range. From combined theoretical analysis and obtained experimental results, it is shown that the best characteristics for the mentioned criteria in the frequency range of 100–700 Hz are possessed by oscillatory displacement receivers based on heavy stethoscopic sensors with a microphone in the neck, as well as by dynamic force receivers based on heavy sensors with a longitudinally deformed piezotransducer between the surface of the body and the sensor housing.