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Game audio part 1: Voices and listenersToolbox
Figure 1: Audio mixing
superimposes waves,
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ǁistinct sounǁs ǹrom one
Ԇʤoiceԇӗ ƹut theʰ ƃȢȢ come
ǹrom the sƃme ǁirectionӝ
An intelligent use of sound can transform how a
player interacts with a game. Simon explains allecades ago, Apple and ZX
Spectrum programmers built
up sounds by toggling a single
bit of hardware connected to a
speaker. My 1983 Spectrum game
Gold Mine mimics the sound of digging with
a one-bit beeper. Imagination was required,
and back then, sound generation stalled the
&38. The multichannel sound chips of s
consoles and home computers helped out
later, by buzzing to order while the processor
attended to graphics or gameplay.
These chips played three or four buzzy notes
or ‘voices’ at a time, with crude volume and
pitch controls. A ‘noise generator’ mimicked
rough hissing and explosions. &ommodore’s 6I'
chip sounded superior because it had a filterGame audio part 1:
Voices and listeners
D
to smooth out the Magged clicks. 6imilar filters
are still used to vary the tone of modern game
sounds, to hint when the source is distant
or partly blocked, mimic concussion, or just
add variety.PRINCIPLES OF SOUND
Sound is a form of vibration. The rate of
vibration, measured in cycles per second or
Hertz and known as frequency, determines the
perceived pitch, with shorter cycles giving higher
notes. Intensity, or wave height, determines
volume. Vary these parameters fast enough,
and any sound can be synthesised. Adding
vibrations together creates chords, or the
impression of several sounds playing at once.
Figure 1 shows a combined wave at the top,
and two components, which will be heard as
distinct tones three octaves apart, in the lower
rows. (lectronic or digital filters sift out tones of
differing freTuencies, though the separation is
rarely as precise as shown here.CURVES OF PERCEPTION
Computers measure time and intensity
linearly, but brains deal in relative differences.
Audio systems and their designers must heed
this, or players will get confused.
In Figure 2, dark bars represent changes
that sound smooth to the ear. Bigger values
need bigger changes to give the same
apparent interval. The lighter bars are linear
to the computer, but the leftmost stepsAUTHOR
SIMON N GOODWIN
Simon N Goodwin has been making games and audio
tech professionally since 1979, including twelve years
as Codemasters’ Principal Audio Programmer.