1. OBJECTIVES :
o What is sound and digital audio.
o How sound is digitized.
o How digital audio is process and stored.
o How to use digital audio in multimedia
product.
AUDIO

2. INTRODUCTION TO SOUND
• Vibrations in the air create waves of
pressure that are perceived as sound.
• Sound waves vary in sound pressure level
(amplitude) and in frequency or pitch.
• Sound pressure levels (loudness or volume)
are measured in decibels (dB).

3. CHARACTERISTICS
Based on 2 things :
o Amplitude
- Power or intensity of the sound.
- Louder sound, higher amplitude.
o Frequency
- The rate at which sound is measured.
- Measure in cycles per second or hertz (Hz).
- Higher frequency, clearer and sharper the sound.

4. VOICE, MUSIC AND
SOUND EFFECT
o Voice define as talking, not singing.
o Music can be created from human singing or
musical instruments.
o Sound effect can be voice or music but often
created by natural events such as a door slam,
shouting etc.

5. DIGITAL AUDIO
• The quality of digital recording depends on
the sampling rate (or frequency), that is, the
number of samples taken per second.
• Three sampling frequencies most often
used in multimedia are
• 44.1 kHz (High quality music – CD quality)
• 22.05 kHz (good voice and acceptable music)
• 11.025 kHz (Voice quality )

6. AUDIO APPLICATIONS
o MP3 (Motion Picture Expert Group Layer 3
format)
− MPEG Audio Layer 3
− High quality
− Small file size
− Popular for sound transmission on the Internet
o Wave : not compress, large file sizes.

7. DIGITAL AUDIO FILE
Extension Platform Using:
.aif Mac, SGI Audio
.aifc Mac, SGI Audio (Compressed)
.au Sun, NeXT ULAW audio data
.mov Mac, Win QuickTime video
.mpeg All MPEG Video
.wav Win WAV Audio

8. CALCULATE SIZE OF AUDIO FILE

9. CALCULATE SIZE OF AUDIO FILE
- High quality music 44KHz, 16 bit, stereo, 10 MB
per minutes = 61 minutes total.

10. USING AUDIO IN
MULTIMEDIA
o Used best recording available for
audio capture.
o Use quiet room reduce background
noise.

11. USING AUDIO IN
MULTIMEDIA
o Choice to on or off the audio.
o Can be used to repeat content
and to enhance it.
o Used to narrate specific elements
of graphics (diagrams, charts,
graph).

12. USING AUDIO IN MULTIMEDIA
o Copyright consideration:
- Need to ask owner if it copyright.
- Safe way to generate original music/sound
yourself, purchase or pay people to do it.
- Can ask music students or musician to create
the music.

13. Adding Sound to Multimedia Project
• File formats compatible with multimedia
authoring software being used.
• Sound playback capabilities offered by end
users’ systems must be studied.
• The type of sound, whether background music,
special sound effects, or spoken dialog, must be
decided.

14. Adding Sound to Multimedia
Project (continued)
• Create or purchase source material.
• Test the sounds to be sure they are timed
properly with your project.

15. • Keeping track of your sounds
– Audio CDs
•The Red Book (or ISO 10149) standard is a
standard for digitally encoding high-quality stereo.
•For this standard, the digital audio sample size is
16 bits and the sampling rate is 44.1 KHz.
Adding Sound to Multimedia
Project (continued)

16. • The speed at which most animations and
computer-based videos play depends on the
user’s CPU.
• Copyrighted material should not be recorded or
used without securing appropriate rights from
the owner or publisher.
Adding Sound to Multimedia Project
(continued)

17. LINK / WEBSITE
Streaming Audio:
o Apple QuickTime
o Real
o SHOUTcast
o Spacial Audio
o Streaming Audio Tutorial
o Streaming Media World