1. Interactive Media Products - The Use of Sound
All You Need To Know Volume 1, Issue 1
Understanding the use of sound in interactive media products
Waveforms
Special points of
Sound is
interest:
produced when
 Theory of Sound something
vibrates. The
 Basics of Sound vibrating body
Recording causes the
medium
 Analogue versus around it to vibrate. Vibrations in air are called traveling longitudi-
Digital nal waves, which we can hear. Sound waves consist of areas of
high and low pressure called compressions. Shown in the dia-
 Applications
gram on the right is a traveling wave. The shaded bar above it
 Use of Sound represents the varying pressure of the wave. Lighter areas are
low pressure and darker areas are high pressure.
Amplitude
The amplitude is a variable characterizing an oscillation. It gives
the deflection of a physical quantity from its neutral position (0-
point) up to a positive or negative value.
The amplitude is expressed in a physical quantity − for example,
as voltage, sound pressure, etc.
Amplitudes are expressed either as instantaneous values or
mostly as peak values.
Amplitude is the variation or displacement of a wave from its
mean value. With sound waves, it is the extent to which air parti-
cles are displaced, and is experienced as the loudness of a
sound.
Frequency
Sound is made up of changes in air pressure in the form of
waves (See waveforms). Frequency is the property of sound that
most determines pitch. The frequencies that an ear can hear are
limited to a certain range of frequencies.
Decibel Levels (dB)
Our ears detect changes in volume in a non-linear fashion. A
decibel is a logarithmic scale of loudness. A difference of 1 deci-
bel is perceived as a minimum change in volume, 3 dB is a mod-
erate change, and 10 decibels is perceived by the listener as a
doubling of volume. Decibels are designated by the letters: dB
Examples:
0 dB is the threshold of hearing
Whisper: 15-25 dB
Background noise: about 35 dB
Normal home or office background: 40-60 dB
Normal speaking voice: 65-70 dB
Orchestral climax: 105 dB
Live Rock music: 120 dB+
Pain Threshold: 130 dB
Jet aircraft: 140-180 dB

2. Sound Generator Pitch Page 2
A sound generator is a vibrat- The sensation of a frequency
ing object which produces a is commonly referred to as the Hertz
sound via sound waves. A pitch of a sound. A high pitch
sound generator is an object sound corresponds to a high Sound travels through air as
that makes sounds. These frequency sound wave and a waves of increasing and de-
sounds may be produced in a low pitch sound corresponds creasing changes in the pres-
nearly infinite number of ways, to a low frequency sound sure of the air. The number of
ranging from a foot stomping wave. complete sound waves moving
on the floor to a fire engine past a point is called the fre-
siren. Regardless of the origin Frequency quency, which is measured in
of the sound, it is always the hertz (Hz).
As a sound wave moves
same thing — vibrations in the
through a medium, each parti-
air that make a pattern recog-
cle of the medium vibrates at
nizable by aural senses. While
the same frequency. This is
the ways to make sound are
sensible since each particle
nearly limitless, practically all
vibrates due to the motion of
sound-generating objects fall
its nearest neighbor. The first
within two main categories:
particle of the medium begins
single-tone and multi-tone.
vibrating, at say 500 Hz, and
Each of these processes
begins to set the second parti-
makes a full and complete
cle into vibrational motion at
sound pattern, but in different
the same frequency of 500
ways.
Hz.
Basics Of Sound Recording
Microphones ground noise or hiss. On the
other hand, a very high level
Any sound from the real world signal can cause distortion,
must first be converted into an
whatever the control setting.
electrical signal by means of a
microphone. All microphones Most types of analogue audio
contain some form of dia- mixer or mixing desk have a
phragm that moves under the microphone input and a line
influence of the sound pres- input on each channel. Alt-
sure waves. This is either part hough the level of each sound
of a capacitor, as in a capaci- source can be adjusted by
tor or condenser microphone, means of a channel fader, the
or is mechanically linked to a ‘default’ gain of a channel is
coil, as in a moving-coil micro- set by additional controls,
phone. usually of the rotary type.
A capacitor microphone usual- Mono & Stereo
ly has a built-in amplifier, re-
quiring a battery inside the Care must be taken to ensure
that those with mono equip-
microphone or an external
source of power. In a profes- ment can hear everything in
sional studio, the mixing desk your recordings. It’s very easy
to create wonderful stereo,
provides phantom power
along the microphone’s con- containing out-of-phase com-
necting cable. ponents, which can’t be heard
in mono. A mono output can
Mixers & Signal Levels be obtained from a stereo
mixing desk by simply combin-
Most analogue audio devices ing the left and right hand
only accept signals within a channels via a buffer amplifier
given range. If the applied
and a 6 dB attenuator or pad.
signal is too low you must turn
up the volume or gain control,
possibly introducing back-

3. Volume 1, Issue 1 Page 3
Analog Vs. Digital Sound Recording
An analog recording is one Examples of properties that recorded onto a digital storage
where a property or character- are modified are the magneti- medium such as a compact
istic of a physical recording zation of magnetic tape or the disc or hard disk.
medium is made to vary in a deviation of the groove of a
manner analogous to the vari- gramophone disc from a
ations in air pressure of the smooth, flat spiral track.
original sound. Generally, the
air pressure variations are first A digital recording is produced
converted into an electrical by converting the physical
properties of the original
analog signal in which either
the instantaneous voltage or sound into a sequence of
current is directly proportional numbers, which can then be
stored and read back for re-
to the instantaneous air pres-
sure. The variations of the production. Normally, the
electrical signal in turn are sound is transduced to an
analog signal in the same way
converted to variations in the
recording medium by a record- as for analog recording, and
ing machine such as a tape then the analog signal is digit-
ized, or converted to a digital
recorder or record cutter—the
variable property of the medi- signal, through an analog-to-
um is modulated by the signal. digital converter and then
Sound In Interactive Media Products
Sound is used in plenty of plosions, dialogue etc. This
media applications such as adds to the excitement and
DVD interfaces, video games, realism of the current video
mobile phones etc. Concerning games on sale.
DVD interfaces, sound is used
in many different ways. For Mobile phones are potentially
one of the greatest of inven-
example, the title screen may
include the soundtrack or tions ever created. Now with
quotes of the movie to add the new iPhone 5 released,
the realization of endless pos-
drama or suspense to the
audience. It also may make a sibilities concerning mobile
noise when the cursor have phones seems phenomenal.
However, since the first re-
moved from one selection to
another. This noise happens in lease of even telephones they
plenty of other applications have always made a sound
that indicates someone is
and is primarily used to inform
the user that they have done trying to contact them. Nowa-
something. Although not a days, ringtones for mobiles
can be set to almost anything.
sound, DVD interfaces also
usually allow the audience to But also, different sounds or
choose the subtitled option for noises can be used for differ-
ent notifications on a phone.
the duration of the film. Simi-
lar to DVD interfaces, video For example there can be dif-
games regularly contain sound ferent sounds for phone calls,
text messages, Twitter/
in main menu scenarios, most-
ly for the same reason of FaceBook notifications etc.
DVD’s. However, for example a
‘shooting’ game will have plen-
ty of sound during gameplay.
Such as: gun shots, cries, ex-