Directivity coefficient  --  To make a comparison between various microphones, this term was introduced to indicate the power output of a nondirectional mike in relation to a directional mike of equal sensitivity in a diffuse sound field. An ideal cardioid mike has a DC of 3. Since the intensity of sound decreases as the square of the distance, the cardioid mike may be used at a distance of 1.7 times farther than a nondirectional mike with the same amount of disturbing ambient noise.