Page 36 - DCAP303_MULTIMEDIA_SYSTEMS

Multimedia Systems

notes introduction

Sound is perhaps the most important element of multimedia. It is meaningful “speech” in any
language, from a whisper to a scream. It can provide the listening pleasure of music, the startling
accent of special effects or the ambience of a mood-setting background. Sound is the terminology
used in the analogue form, and the digitized form of sound is called as audio.
Sound is produced when waves of varying pressure travel though a medium, usually air. It
is inherently an analogous phenomenon, meaning that the changes in air pressure can vary
continuously over a range of values.

Modern computers are digital, meaning they operate on discrete values, essentially the binary
ones and zeroes that are manipulated by the Central Processing Unit (CPU). In order for a
computer to manipulate sound, then, it needs to convert the analogue sound information into
digital format.

3.1 Multimedia system sounds

The multimedia application user can use sound right off the bat on both the Macintosh and on
a multimedia PC running Windows because beeps and warning sounds are available as soon as
the operating system is installed. On the Macintosh you can choose one of the several sounds
for the system alert.

There are still more choices of audio if Microsoft Office is installed. Windows makes use of WAV
files as the default file format for audio and Macintosh systems use SND as default file format
for audio.
In windows system sounds are WAV files, reside in the Windows\Media
subdirectory.

3.2 Digital audio

Digital audio is created when a sound wave is converted into numbers—a process referred to
as digitizing. It is possible to digitize sound from a microphone, a synthesizer, existing tape
recordings, live radio and television broadcasts, and popular CDs. You can digitize sounds from
a natural source or pre-recorded.
Digitized sound is sampled sound. Every nth fraction of a second, a sample of sound is taken
and stored as digital information in bits and bytes. The quality of this digital recording depends
upon how often the samples are taken.

3.2.1 preparing Digital audio files
Preparing digital audio files is fairly straight forward. If you have analogue source materials,
music or sound effects that you have recorded on analogue media such as cassette tapes.
• The first step is to digitize the analogue material and recording it into a computer readable
digital media.
 It is necessary to focus on two crucial aspects of preparing digital audio files: Balancing
the need for sound quality against your available RAM and Hard disk resources.
 Setting proper recording levels to get a good and clean recording.
Remember that the sampling rate determines the frequency at which samples will be drawn for
the recording. Sampling at higher rates more accurately captures the high frequency content of
your sound. Audio resolution determines the accuracy with which a sound can be digitized.

30 LoveLy professionaL University