The present invention relates to a system for detection of low frequency power for diagnosing of coronary artery disease (CAD), comprising: an acoustic sensor adapted to be placed on the chest of a patient, and to generate acoustic signals S A ; at least one memory adapted to store acoustic signals S A from the acoustic sensor; a control unit adapted to receive said acoustic signals S A ; the control unit further comprises: an identification unit adapted to identify diastolic or systolic periods in a predetermined time period of the stored acoustic signals S A , and to generate a period signal S P indicating said identified periods; a filtering unit adapted to apply at least one filter to said identified periods and to generate a low frequency band signal S LFB indicating low frequency bands of said identified periods; a calculation unit adapted to estimate the power in said low frequency band of said identified periods, to calculate a low frequency power measure based upon said estimated power and to generate a low frequency power measure signal S LFP indicating said low frequency power measure. The invention also relates to a stethoscope and a method for detection of low frequency power.