Humans can detect interaural timing differences as small as ten to twenty microseconds

Evidence

By comparing the timing and intensity of a sound at each ear, listeners can locate its source on the horizontal plane, and exploit these differences to hear out signals in background noise—an important component of ‘cocktail party listening’. Sensitivity to interaural time differences (ITDs) in particular has received much attention, due in part to the exquisite temporal performance observed; for sound frequencies lower than about 1.3 kHz, ITDs of just a few tens of microseconds are discriminable, observed both at the neural and behavioural levels. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2949

Humans are relatively sensitive to small changes in ITD. The value of the JND of the ITD depends on the ITD itself, on the level of the signal, and on the temporal and spectral content of the signal. In the best case, with relatively broadband stimuli which have strong temporal envelopes, and with base ITD corresponding to directions near the median plane, the JND of ITD is of the order of the 10 μs to 20 μs (Blauert, 1996; Hafter and De Maio, 1975). — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1432

By comparing the timing and intensity of a sound at each ear, listeners can locate its source on the horizontal plane, and exploit these differences to hear out signals in background noise—an important component of ‘cocktail party listening’. Sensitivity to interaural time differences (ITDs) in particular has received much attention, due in part to the exquisite temporal performance observed; for sound frequencies lower than about 1.3 kHz, ITDs of just a few tens of microseconds are discriminable, observed both at the neural and behavioural levels. Sensitivity to ITDs decreases with ageing (Herman et al. 1977 ; Abel et al. 2000 ; Babkoff et al. 2002 ), and is typically impaired in hearing loss, albeit variability across individuals and aetiologies (see Moore et al. 1991 , for review), with reduced sensitivity most apparent when trying to localise sources in background noise (Lorenzi et al. 1999 ). ITD processing may also remain impaired following surgery to correct conductive hearing loss (Wilmington et al. 1994 ), and sensitivity to ITDs is typically poor in users of hearing technologies such as bilateral cochlear implants (CIs). — Dijk, Pim van, Physiology, Psychoacoustics and…, 2951

Categorization

• CANDY: The ‘tens of microseconds’ ITD discrimination is a striking, tweetable fact about auditory acuity.
• XREF: The ‘cocktail party’ framing connects to broader psychoacoustics of auditory scene analysis and Bregman’s work. — connects to: Just-noticeable interaural delay is about 50 microseconds below 1.5 kHz; The ear detects binaural delays finer than individual neuron timing supports; Head size alone predicts interaural time differences well across azimuth angles (+4 more)
• corroborated: 6 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 2949; Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1432; Dijk, Pim van, Physiology, Psychoacoustics and…, 2951

Broader Connections

• The brain measures interaural delay via coincidence-detector neurons and delay-line axons #expands (0.85)
• Head size alone predicts interaural time differences well across azimuth angles #corroborates (0.80)