The sound inside the human body, such as heartbeat, bowel sounds, wet rales, etc., and even the sound of blood flow is not very "heard". The reason is that the audio is too low or the volume is too low, or is obscured by the noisy environment. The principle of the stethoscope is that the vibration transmission between substances participates in the aluminum film in the stethoscope, and the air alone changes the frequency and wavelength of the sound, reaching the "comfortable" range of the human ear, while shielding other sounds and "hearing" more. clear.
