Wireframe_-_Issue_23_2019

wfmag.cc \ 33

Game audio part 1: Voices and listeners

Toolbox

 Figure 2: Human

perception is

non-Ȣineƃrӗ so gƃins

must ƹe muȢtipȢieǁӗ or

ǁeciƹeȢ ƃttenuƃtions

ƃǁǁeǁ ǹor miʯing to

sounǁ reƃȢisticӝ

by fiddling with noise and tone controls, and

wrapping the lot up in machine code which the

game could call  or  times a second to keep

the bleeps coming.

The Commodore Amiga introduced sample

replay, then some audio engineers specialised

in recording or replay. There were still only four

‘voices’ but they could

sound like anything you

could spare memory to

describe. Any sequence

of samples, played at a

steady rate, generated a

correspondingly shaped waveform. Varying the

rate varied the pitch. PC sample replay cards like

the Sound Blaster followed suit.

 Recorǁing engine noises in the

ƃnechoic chƃmƹer ƃt the Ãotor

Žnǁustrʰ Reseƃrch ssociƃtionӝ

ěhe mƃssiʤe ǹƃn cȢeƃrs out the

smoȟe ƹetʥeen tƃȟesӝ

HOOT ORDER
Computers had speakers
long before they had
displays. Early British
computers made in the late
1940s and 1950s featured
what Alan Turing called a
‘hoot order’ which could
make sounds to alert – or
entertain – their operators.
In 1951, Christopher
Strachey ported a draughts
player from the Pilot ACE
computer and added code
to play the national anthem
on the hooter of the
Manchester Mark 2.
are barely perceptible to humans, and
Merky later. 'esigners favour psychoacoustically
weighted units like decibels or semitones,
and programmers must understand both.
2ne decibel of change sounds the same
amount wherever you start.
Pitch is the logarithmic counterpart to
frequency, which doubles across any twelve
consecutive piano keys (semitones). Brightness
is perceived similarly. Whenever a game models
these properties, it needs
to follow the human
curves rather than the
electronic ones, or fades
sound unnatural, and
players will struggle to
determine the direction, distance, and speed of
the game objects they’re trying to catch or avoid.

FILTERING FREQUENCIES
Figure 3 shows how filters divvy up sound.
0ix the low-pass and high-pass bands to
exclude frequencies in the middle, or emphasise
the passband component for the opposite
effect. 9arying the gap width – known as
resonance, or sometimes Ȇ4’ – selects Must
the frequencies you wish to catch or lose.
6weeping the centre freTuency fc) of filters
applied to output for each ear, rapidly up and
down in opposite directions left and right, gives
a di]]ying effect that makes players think their
heads are spinning.
At first, one engineer did all the audio Mobs

• seTuencing music, creating sound effects

“Vary these parameters

fast enough, and any

sound can be synthesised”