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Physics

Interaural Time Difference (ITD)

Quick fact

The maximum interaural time difference for a human head is about 0.7 milliseconds, corresponding to sound arriving directly from the side. Despite its tiny duration, the brain can resolve ITDs of just 10–20 microseconds, equivalent to a spatial angle of about 1–2 degrees.

Why this is interesting

You can detect a time difference as small as 10 microseconds—that's less than the time it takes light to travel 3 kilometers. How does your brain use this almost unimaginably short delay to tell where a sound is coming from?