Spatial Audio Processing: MPEG Surround and Other Applications

3.3 Spatial hearing basics

In the previous section, it was described how various stages of the auditory system respond to ITDs, ILDs and their resemblance to the cross-correlation function. In this section, the relation between physical attributes of sound sources and these localization cues will be described.

3.3.1 Spatial hearing with one sound source

The simplest listening scenario is when there is one sound source in free-field. Free-field denotes an open space with no physical objects from which sound is reflected. Anechoic chambers are rooms frequently used for experimentation under free-field-like conditions. Due to their highly sound absorbent walls there are virtually no reflections, similarly to free-field. Localization denotes the relation between the location of an auditory object and one or more attributes of a sound event. A sound event denotes sound sources and their corresponding signals responsible for the perception of the auditory object. For example, localization may describe the relation between the direction of a sound source and the direction of the corresponding auditory object. Localization blur denotes the smallest change in one or more attributes of a sound event such that a change in location of the auditory object is perceived. For sources in the horizontal plane, localization blur with respect to direction is smallest for sources in the forward direction of a listener. It is slightly larger for sources behind the listener and largest for sources to ...