Interaural intensity difference

Interaural intensity differences (IIDs), better called interaural level differences (ILD), are differences of the soundpressure level arriving at the two ears; and are important cues that men and animals use to localise higher frequency sounds. The interaural time difference is another source of information for sound localization. Our ears are only sensitive to sound pressure changes.

Neurons sensitive to ILDs are excited by stimulation of one ear and inhibited by stimulation of the other ear, such that the response magnitude of the cell depends on the relative strengths of the two inputs, which in turn, depends on the sound intensities at the ears.

In the auditory midbrain nucleus, the inferior colliculus (IC), many ILD sensitive neurons have response functions that decline steeply from maximum to zero spikes as a function of ILD. However, there are also many neurons with much more shallow response functions that do not decline to zero spikes.