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

INTRODUCTION TO SOUND

• Vibrations in the air create waves ofpressure 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).

CHARACTERISTICSBased 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.

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.

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 )

AUDIO APPLICATIONSo 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.

DIGITAL AUDIO FILEExtension 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

CALCULATE SIZE OF AUDIO FILE

CALCULATE SIZE OF AUDIO FILE

- High quality music 44KHz, 16 bit, stereo, 10 MB per minutes = 61 minutes total.

USING AUDIO IN MULTIMEDIA

o Used best recording available for audio capture.

o Use quiet room reduce background noise.

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).

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.

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.

Adding Sound to Multimedia Project (continued)

• Create or purchase source material.

• Test the sounds to be sure they are timed properly with your project.

• 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)

• The speed at which most animations andcomputer-based videos play depends on theuser’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)

LINK / WEBSITE

Streaming Audio: o Apple QuickTime o Real o SHOUTcast o Spacial Audio o Streaming Audio Tutorial o Streaming Media World