The measure of the difference in signals received by two ears of a person. IACC values range from -1 to +1. A value of -1 means the signals are identical, but completely out of phase. +1 means they are identical, and 0 means they have no correlation at all. The IACC will be nearly +1 for mono sources directly in front of or behind the listener, with lower values if the source is off to one side. IACC values are of interest to acousticians as a number of researches have found that large IACC values correspond to greater degrees of envelopment and overall more enjoyable listening experience in auditoriums.