Intensity Stereo Coding(ISC) is an audio compression based on the localization of the sound source. The sound that hits the human ear is not precisely determinable in direction, and moreover, the determination of direction depends on the frequency level. Intensity Stereo Coding takes advantage of this effect by reducing the data rate at which sound is emitted, at which no or only slight quality degradation is perceptible.
Interaurally, humans can hear time differences, Inter-Aural Time Differences (ITD), and level differences, Inter-Aural Amplitude Differences( IAD). The detectable time differences have a higher impact at lower frequencies than at high frequencies. It is different for the audible level differences, which are more dominant at higher frequencies than at lower frequencies. Therefore, Intensity Stereo Coding (ISC) combines the frequency components of the audio stereo channels with higher frequencies into one channel, eliminating the time or phase differences. In order to be able to reconstruct the level differences during the reconversion, some additional information is also transmitted.