Interaural Time Delay and Interaural Intensity Difference:

Our ability to determine location of sounds is rooted in what can be boiled down to a few key points (and for the sake of this presentation will be kept very basic):

Interaural Time Difference (ITD) – Localization determined based on the time a sound takes to arrive at each ear

Interaural Intensity Difference (IID) - Localization determined based on the intensity of a sound arriving at each ear

Also known as Interaural Level Difference (ILD)

Each of these contributions can be roughly boiled down to the following*:

ITD cues contribute mostly up to approximately 800hz and then share with IID through approximately 1400hz where IID then takes over

* This is a summary of various research. There is additional useful information here: ITD and IID Cues

Below is a graphical representation of ITD/IID and the area where they have some overlap:

It should be noted this section does not consider any sound source other than laterally in front of the listener. For further reading on the topic, also consider the impact of the Head Related Transfer Function (HRTF) and Head Related Impulse Response (HRIR) as the “Cone of Confusion”.