a tone generated in the ear that is produced when two primary tones (i.e., two tones differing in frequency) are presented simultaneously. For example, under certain conditions a 1000 Hz tone and a 1200 Hz tone will produce audible combination tones whose frequencies are 200 Hz (a difference tone) and 800 Hz (a cubic difference tone). Most combination tones are produced by nonlinear distortion that occurs within the cochlea.