12.7 Summary of Section 12

For precise localisation of a sound source, binaural cues are required.

Two types of binaural cue are used to localise non-continuous sounds in the horizontal plane: interaural time differences, which are most efficient for low-frequency sounds (20–1500 Hz) and interaural intensity cues, which are important for high-frequency sounds (1500–20 000 Hz). The frequency responses in the superior olive reflect these differences. The medial superior olive includes neurons that are responsive to low-frequency inputs, while the cells of the lateral superior olive are most sensitive to high-frequency stimuli.

The mechanism involved for the detection of interaural time differences is believed to involve a series of delay lines and coincidence detectors.

For localisation of continuous tones, interaural phase differences are used.

Information about the location of a signal in the vertical plane is provided by the pinnae.

We are able to judge the distance to a sound source using cues related to the decay of the signal with distance. Both the SPL and the spectral components of a signal are dependent on the distance between the signal and the listener.