Hearing in Complex Environments

64 Interaural Level Difference

Learning Objectives

Know that interaural level difference (ILD) is a binaural cue.

Be able to explain why ILD is useful for high-frequency sounds only (frequency-dependent).

Understand the difference between ILD (higher frequency) and ITD (below about 1500 Hz).

If a sound comes from an off-center location, it creates two types of binaural cues: interaural level differences and interaural timing differences. Interaural level difference refers to the fact that a sound coming from the right side of your body is more intense at your right ear than at your left ear, and vice versa for sounds from the left, because of the attenuation of the sound wave as it passes through your head.

 

Fig.7.3.1. ILD. The interaural level binaural cue only happens with high frequencies. In the image above, the person only experiences an acoustic shadow produced by this cue with a high frequency, but not a low one (<1000 Hz). (Credit: Jarod Davis. Provided by: University of Minnesota. License: CC-BY 4.0)

Interaural level difference (ILD) is a binaural cue for high-frequency sounds only. High frequency sounds have short wavelengths, so the head casts an acoustic shadow and sounds are quieter in the ear away from the sound. Below about 1000 Hz, there is no ILD because the head is small compared to the wavelength of the air pressure perturbation. The sound sweeps on by without really noticing the head. ILDs can be as big as 20dB for some frequencies; they depend both on frequency and on the direction that sounds are coming from. ILDs are more useful at higher frequencies; ITDs stop being useful at about 1500 Hz.

Interaural level difference refers to the fact that a sound coming from the right side of your body is more intense at your right ear than at your left ear because of the attenuation of the sound wave as it passes through your head. Interaural timing difference refers to the small difference in the time at which a given sound wave arrives at each ear. Certain brain areas monitor these differences to construct where along a horizontal axis a sound originates.

CC LICENSED CONTENT, SHARED PREVIOUSLY

OpenStax, Psychology Chapter 5.4 Hearing
Provided by: Rice University.
Download for free at http://cnx.org/contents/4abf04bf-93a0-45c3-9cbc-2cefd46e68cc@5.103.
License: CC-BY 4.0

Cheryl Olman PSY 3031 Detailed Outline
Provided by: University of Minnesota
Download for free at http://vision.psych.umn.edu/users/caolman/courses/PSY3031/
License of original source: CC Attribution 4.0
Adapted by: Chandni Jaspal

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Introduction to Sensation and Perception by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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