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The purpose of research is increasing the diversity of designs of electronic auscultation systems with measured characteristics and testing.   A series of articles includes the development of a model of an electronic auscultation system, the development of an electronic stethoscope design, the manufacture of an experimental sample, the development of a method for measuring the amplitude-frequency characteristics of electronic and classical stethoscopes, testing the proposed models and methods, and analyzing auscultatory data. The article proposes a method for measuring the frequency response of classical and electronic stethoscopes. The proposed method was tested. The frequency response of classical and electronic stethoscopes was measured. The design of the head of the electronic stethoscope has been improved, the frequency response of the original and improved designs has been compared.   Methods. The studies were based on methods for measuring the frequency characteristics of electroacoustic transducers proposed in interstate standards. On the basis of methods in interstate standards, a simplified method for measuring the amplitude-frequency characteristics of electronic stethoscopes has been developed. The following equipment was used in the study: Type 4227 "Artificial Mouth" emitter from Bruel & Kjaer; measuring condenser microphone "Artificial ear" Type 4146 with a 2CC reference chamber from Bruel & Kjaer; Type 2118 analyzer from Bruel & Kjaer.   Results. The amplitude-frequency characteristics of classical and electronic stethoscopes are obtained. The design of the electronic stethoscope head has  been improved, the amplitude-frequency characteristics of the original and improved designs have been compared.   Conclusion. A method for measuring the parameters of the frequency characteristics of the sound pressure level of classical and electronic stethoscopes is proposed. The method is as close as possible to the standardized methods for monitoring acoustic parameters, while being sufficiently simple and cheap compared to the pressure measurement method, demonstrating the qualitative similarity of the measurement results.

The purpose of research is to increase the diversity of electronic auscultation system designs with measured characteristics and testing.   The series of articles includes the development of a model of the electronic auscultation system, the design of an electronic stethoscope, the manufacture of an experimental sample, the development of a methodology for measuring the amplitude-frequency characteristics of electronic and classical stethoscopes, testing of the proposed models and methods, analysis of auscultative data. The article considers mathematical methods of primary analysis of auscultative data. Recordings of normal and hard breathing were used for the experiment. Frequency, time-frequency and autocorrelation analysis of respiratory sounds was performed.   Methods. The research was based on the theory of digital signal processing. The study uses auscultative data obtained from an experimental sample of an electronic auscultation system. Electronic records of hard (pathological) and normal human breathing over the left middle lung were used. Respiratory noises were converted into digital form with the following parameters: sampling frequency fd = 48 kHz; bit depth n = 24 bits; number of channels 1. To analyze the frequency information content of the recordings, their spectra were constructed. A fast Fourier transform was used to calculate the values in the spectra.  Results. In the presented work, the frequency characteristics of recordings of hard and normal breathing are analyzed. The values of autocorrelation functions are obtained. An author-regression model of the process of normal breathing is obtained. The problem of analytical determination of the model order remains open and requires a separate solution. The resulting model allows you to generate an equivalent breathing noise of inhalation or exhalation when a signal with a uniform is applied to its input.   Conclusion. A sample of the electronic auscultation system has been tested, methods of simplified primary analysis of auscultative data have been proposed. The difference in the results of the treatment of hard and normal breathing has no statistical significance due to the small sample.