A system for detection of frequency power for diagnosing coronary artery disease (CAD), comprising: an acoustic sensor to be placed on the chest of a patient to generate acoustic signals SA: a memory adapted to store acoustic signals SA; a control unit adapted to receive said acoustic signals SA; the control unit comprising: an identification unit to identify diastolic or systolic periods in a predetermined time period and to generate a period signal SP, a filtering unit adapted to apply a filter to said identified periods to generate a low frequency band signal SLFB indicating low frequency bands of identified periods; a calculation unit to estimate the power in said low frequency band of identified periods, to calculate a low frequency power measure and to generate a low frequency power measure signal SLFP. The invention also relates to a stethoscope and a method for detection of low frequency power.