Ears detect direction changes as small as 5 degrees via 50-microsecond delays

Evidence

If a sound source is located not directly in front of our nose, it produces sound signals at our ears that are delayed, one relative to the other. The maximal possible inter aural delay is produced when the sound source is located 90° from frontal incidence. Thus a deviation of the incoming waves for the two sounds of about 21 cm is the maximum possible, corresponding to a delay time of 0.6 ms. The just-noticeable difference in localization, which means the just-noticeable change of the direction of the sound source that is necessary to produce a just-noticeable difference in the sensation of the direction, is about 5° for frontal incidence corresponding to a time delay of about 50 liS. This value can be assumed as being the just-noticeable interaural delay at frequencies below about 1.5 kHz. It should not be confused with temporal resolution, which belongs to the stimulation of only one ear and reaches a much larger value of about 2 ms. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1623

Categorization

• XREF: The order-of-magnitude contrast between 50-microsecond interaural threshold and 2-ms monaural temporal resolution connects to the earlier soundscape work on temporal discrimination. — connects to: Unlike the eye, the ear has no primary directional sensitivity — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1510