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What sort of computations are used for localising sound with the ears, and how does the brain compute the time difference between sounds reaching each ear? I am interested in the specific mechanisms rather than a general account.

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I would focus the question more, and split it into two different ones. Since there is already an answer on sound localisation, I would suggest focusing this question on sound localisation (and making the title obviously reflect that). If you are still interested in velocity then I would ask that as a separate question on estimating velocity with a title that reflects the particulars. –  Artem Kaznatcheev Nov 13 '13 at 16:48
    
Thanks I will edit it accordingly, sorry for the lack of clarity. –  AAM Nov 13 '13 at 17:51
    
I am still skeptical of the "without equations" bit, but I changed my downvote to an upvote since this is a focused question now. –  Artem Kaznatcheev Nov 13 '13 at 20:57
    
Thank you for the guidance, I am new to this forum and your rules so I appreciate the advice! I suppose what I mean is without formally (consciously?) going through them in your head - I presume approximations of the terms in the equations must exist. Perhaps the phrasing is a bit off, but I don't know the first thing about how it's done, which is why I'm asking. –  AAM Nov 13 '13 at 21:35

2 Answers 2

From the physics(acoustics) perspective, the sensory input changes depending upon pitch. When you hear a sound that is high-pitched, your head blocks the sound wave, creating a sound shadow for the ear on the opposite side of your head from the sound source. This sound shadow means that your ears hear the sound at two different volumes, which the brain then uses to calculate direction.

For low-pitched sound, the distance between your ears creates a phase difference between the sound perceived in each ear. And that phase difference indicates sound direction. If I understand your question, it centered upon the brain's processing of this phase difference information.

For mixed-pitch sounds, you utilize both, which makes complex sounds even easier to locate.

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Some neuroscience papers on sound localization:

  1. Joris Philip X, Smith Philip H, and Yin Tom C.T Coincidence Detection in the Auditory System // Neuron (1998)
  2. Agmon-Snir Hagai, Carr Catherine E. and Rinzel John The role of dendrites in auditory coincidence detection // Nature (1998)
  3. Trussell Laurence O. Synaptic mechanisms for coding timing in auditory neurons // Annual Review of Physiology (1999)
  4. Grothe B., Pecka M., & McAlpine D. Mechanisms of Sound Localization in Mammals // Physiological Reviews (2010)
  5. Chen X, Leischner U, Rochefort NL, Nelken I, Konnerth A. Functional mapping of single spines in cortical neurons in vivo // Nature (2011)

Books

  1. Blauert, J.: Spatial hearing: the psychophysics of human sound localization; MIT Press (1983)
  2. Schnupp, Nelken and King: Auditory Neuroscience: Making Sense of Sound, MIT Press, 2011
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Hi, thanks for offering so many sources +1 for that. Perhaps you'd care to write something about what you have found? Answers here should contain some original content and citations.. and welcome :) –  user3543 Nov 14 '13 at 2:38

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