Abstract: This invention is concerned with a method and apparatus for measuring and controlling the quality of physiological acoustic signals, which include tracheal breathing sounds, lung sounds, heart sounds, blood flow sounds, joint sounds, and gastrointestinal sounds. The interface between the skin and the device is carefully controlled to achieve a desirable acoustic coupling. A pneumatic feedback control system automatically adjusts of the pressure applied to the skin; another pneumatic control system adjusts the pressure inside an airtight chamber for housing the acoustic sensor. A processor assesses the signal qualities, such as amplitude and frequency spectrum, and provides feedback controls to the interface if needed. The resulting method and apparatus eliminates operator's variability and acquires physiological acoustic signals with consistent and desirable qualities for various medical diagnostic purposes.