PURPOSE: To preserve recording for objectively displaying lung sound corresponding to the needs on the clinical spot, by mounting a lung sound analyser having function for recording the signals of the lung sound and respiration phase from a detector and displaying the arbitrary parts of said signals on the same time axis.

CONSTITUTION: A lung sound analyser 4 is equipped with an A/D converter 32 for digitalizing the signal of lung sound from a lung sound recorder 3, a demodulator 31 for digitalizing a signal of a respiration phase, a digital memory 33 for recording those data only for a definite time and an operation apparatus 34 for analyzing the content of said memory. The operation apparatus 34 is equipped with a waveform expanding function 34-1 for expanding the acoustic waveform of the signal in the memory, a frequency analyzing function 34-2, an abnormal sound analyzing function 34-3 and a lung sound chart display function 34-4. The waveform expanding function is necessary for extracting and observing the waveform of lung sound having abnormal sound and the frequency analyzing function divides the lung sound at a definite time interval to calculate the frequency component at every section. The abnormal sound analyzing function describes characteristics of the intermittent side noise of fibroid lung and the continuous side noise of asthma.