SINAD is an abbreviation for SIgnal-to-Noise And Distortion. It is a measure of audio quality used in low signal-to-noise ratio situations such as radio communications systems. SINAD is usually performed with a stimulus signal of 400 Hz or 1 kHz.
SINAD is defined as the ratio of the total signal (desired signal plus the sum of all distortion and noise components) to the sum of all distortion and noise components. SINAD can never be less than 1, and is always positive when expressed in dB. SINAD is the reciprocal of THD+N, and can be converted to ENOB.