Spatial Sound for Computer Games and Virtual Reality - Game Sound Technology and Player Interaction: Concepts and Developments - page 290

Figure 2. Evolution of spatial sound implementation in VR and game technology

there. Before it enters the middle ear, the sound
is filtered by the listener's unique ear and head
shape/size. These processes of filtering, along
with internal higher cognitive processes, combine
to infuse the processed sound with a spatial sig-
nature unique to the listener.

two signals). This mechanism is most useful for
frequencies between 20 Hz to 2 kHz. In ITD, sound
coming directly from the right will reach the right
ear 0.6 msec before reaching the contralateral
left (Begault, 1993). The accuracy of the human
auditory system to locate sounds based on ITD
is very impressive, with studies (Begault, 1993)
showing a discrimination of an angle as small as
1º or 2º (which translates to a time difference of
about 11 µsec!), depending on the position. Refer
to Figure 3.
However, what happens when sounds are
continuous and we do not have the onset informa-
tion such as in sudden, brief sounds? A slight
variant of ITD is used instead by the human audi-
tory system. In such cases, the phase discrepancy
between the right and left ears is analyzed and
the location of a sound source is determined. In
other words, the peak of a wave-cycle reaches the
right ear before it reaches the left. From this
method ensues another problem however. For
high frequencies (in humans this would be around

Human Auditory system-sound
Localization Mechanisms

The basic (physiological-based) understanding of
sound localization in humans is one comprising
two distinct categories-the first dealing with the
horizontal plane (left, right, front, back) and the
other with the vertical plane (above and below the
head position). With regard to sound localization
on the horizontal plane, a number of factors come
into play. One of the most obvious mechanisms
is ITD where a sound will reach one ear before
it reaches the other (the speed of sound remains
constant, however, apparent differences in arrival
time results from phase differences between the