Crestron
Surround Sound
Primer
Interaural Intensity Difference
For example, a sound coming from the extreme left has a lowered
intensity in the right ear in addition to a slight time delay. The reduced
intensity is the additional distance plus the effect of the acoustical
shadow. The amount of this effect depends on frequency, and is useful
for high frequencies up to wavelengths twice the distance between the
ears (about 1 kHz). Lower frequencies, with longer wavelengths, bend
around obstructions.
Pinna Filtering
The pinna structure is the outer part of the ear. Its forward pointing
position and complex curves affect the way sound is heard. A sound is
coming from behind or above bounces off the pinna in a different way
than from in front or below. When the indirect (reflected) sounds from
the pinna combine with the direct sounds, the wavelengths of the sound
are altered.
Pinna Filtering
The brain, interpreting the altered sounds, produces directional
information. To provide additional cues, small head movements
(motion parallax) allow the brain to judge relative differences.
The Precedence Effect
The precedence effect is a listening strategy unconsciously used to cope
with distorted localization cues in a confined space. Localization
judgments are based on the first arriving sound waves at the beginning
of a sound. This strategy is known as the precedence effect, because the
Primer – DOC. 6122
Surround Sound
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