# Show Reference: "Sound localization"

Sound localization In The Human Auditory System Fundamental Organization and Clinical Disorders, Vol. 129 (2015), pp. 99-116, doi:10.1016/b978-0-444-62630-1.00006-8 by John C. Middlebrooks edited by Michael J. Aminoff, FranÃ§ois Boller, Dick F. Swaab
@inbook{middlebrooks-2015,
author = {Middlebrooks, John C.},
booktitle = {The Human Auditory System Fundamental Organization and Clinical Disorders},
citeulike-article-id = {13532967},
doi = {10.1016/b978-0-444-62630-1.00006-8},
editor = {Aminoff, Michael J. and Boller, Fran\c{c}ois and Swaab, Dick F.},
isbn = {9780444626301},
keywords = {biology, ssl},
pages = {99--116},
posted-at = {2015-03-04 09:40:59},
priority = {2},
publisher = {Elsevier},
series = {Handbook of Clinical Neurology},
title = {Sound localization},
url = {http://dx.doi.org/10.1016/b978-0-444-62630-1.00006-8},
volume = {129},
year = {2015}
}



In mammals, different neurons in the lateral superior olive (LSO) are tuned to different ILDs.

In mammals, different neurons in the medial superior olive (MSO) are tuned to different ITDs.

The model of biological computation of ITDs proposed by Jeffress extracts ITDs by means of delay lines and coincidence detecting neurons:

The peaks of the sound pressure at each ear lead, via a semi-mechanical process, to peaks in the activity of certain auditory nerve fibers. Those fibers connect to coincidence-detecting neurons. Different delays in connections from the two ears lead to coincidence for different ITDs, thus making these coincidence-detecting neurons selective for different angles to the sound source.

ITD and ILD are most useful for auditory localization in different frequency ranges:

• In the low frequency ranges, ITD is most informative for auditory localization.
• In the high frequency ranges, ILD is most informative for auditory localization.

Sound source localization based only on binaural cues (like ITD or ILD) suffer from the ambiguity due to the approximate point symmetry of the head: ITD and ILD identify only a `cone of confusion', ie. a virtual cone whose tip is at the center of the head and whose axis is the interaural axis, not strictly a single angle of incidence.

Spectral cues provide disambiguation: due to the asymmetry of the head, the sound is shaped differently depending on where on a cone of confusion a sound source is.

Acoustic localization cues change from far-field conditions (distance to stimulus $>1\,\mathrm{m}$) to near-field conditions ($\leq 1\,\mathrm{m}$).

There are fine-structure and envelope ITDs. Humans are sensitive to both, but do not weight envelope ITDs very strongly when localizing sound sources.

Recent neurophysiological evidence seems to contradict the details of Jeffress' model.

Some congenitally unilaterally deaf people develop close-to-normal auditory localization capabilities. These people probably learn to use spectral SSL cues.

Humans use a variety of cues to estimate the distance to a sound source. This estimate is much less precise than estimates of the direction towards the sound source.