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TRANSCRIPT
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SoundSession 05
Subject : INF007 / Teknologi Multimedia
Year : 2008
UNIVERSITAS ISLAM NEGERI JAKARTA
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Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
Menunjukkan Penggunaan Suara pada Aplikasi
Multimedia
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Outline Materi
Sound
Waveforms
Analogue to Digital Converter (ADC)
Digital Audio
MIDI (Musical Instrument Digital Interface)
Using Sound
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Sound
Sound are rapid vibrations that are transmitted as variations in airpressure
Sound comprises the spoken word, voices, music and even noise.
It is a complex relationship involving a vibrating object (sound
source), a transmission medium (usually air), a receiver (ear) and aperceptor (brain). Example banging drum.
As the sound vibrates it bumps into molecules of the surroundingmedium causing pressure waves to travel away from the source inall directions
Types of Sound in Multimedia: Speech
Music
Sound Effect
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Waveforms
Sound waves are manifest as waveforms A waveform that repeats itself at regular intervals is
called a periodic waveform
Waveforms that do not exhibit regularity are called
noise
The unit of regularity is called a cycle
This is known as Hertz (or Hz) after Heinrich Hertz
One cycle = 1 Hz
Sometimes written as kHz or kiloHertz (1 kHz = 1000 Hz)
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Waveforms
distance
along waveCycle
Time for one cycle
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The characteristics of sound
waves
Sound is described in terms of two characteristics: Frequency Amplitude (or loudness)
Frequency the rate at which sound is measured
Number of cycles per second or Hertz (Hz) Determines the pitch of the sound as heard by our ears
The higher frequency, the clearer and sharper the sound the higherpitch of sound
Amplitude
Sounds intensity or loudness The louder the sound, the larger amplitude.
In addition, all sounds have a duration and successive musicalsounds is called rhythm
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The characteristics of sound
waves
distance
along wave
Cycle
Time for one cycleAmplitude
pitch
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Example waveforms
PianoPiano
Pan flutePan flute
Snare drumSnare drum
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Capture and playback of digital
audio
Air pressurevariations
Captured viamicrophone
Air pressure
variations
ADC
Signal is
converted into
binary
(discrete form)0101001101
0110101111
Analogueto DigitalConverter
DAC
Converts
back into
voltage
Digital toAnalogueConverter
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e na ogue o g a
Converter (ADC)
An ADC is a device that converts analogue signals into digitalsignals
An analogue signal is a continuous value It can have any single value on an infinite scale
A digital signal is a discrete value It has a finite value (usually an integer)
An ADC is synchronised to some clock
It will monitor the continuous analogue signal at a set rate and
convert what it sees into a discrete value at that specific moment intime
The process to convert the analogue to digital sound is calledSampling. Use PCM (Pulse Code Modulation)
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Digital sampling - Sampling
frequency
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Digital sampling - Sampling
frequency
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Sampling
Two parameters: Sampling Rate
Frequency of sampling
Measure in Hertz
The higher sampling rate, higher quality sound but size storage isbig.
Standard Sampling rate: 44.1 KHz for CD Audio 22.05 KHz
11.025 KHz for spoken
5.1025 KHz for audio effect
Size sample The resolution of a sample is the number of bits it uses to store a
given amplitude value, e.g. 8 bits (256 different values)
16 bits (65536 different values)
A higher resolution will give higher quality but will require morememory (or disk storage)
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Quantisation
Samples are usually represented theaudio sample as a integers(discrete
number) or digital
Sample points
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Calculating the size of digital
audio
Example: Calculate the file size for 1 minute, 44.1 KHz, 16 bits,
stereo sound
Where:
sampling rate is 44,100 Hz duration/time is 60 seconds
resolution is 16 bits
number of channels for stereo is 2
8channelsofnu berresolutiondurationrate
vvv
44100 * 60 * 16 *2
8
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Digital audio editing software
One of the most powerful and professional PC-based packages is a tool called Sound Forge
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Editing Digital Audio
Trimming Splicing and assembly
Volume adjustments
Format conversion
Resampling or downsampling
Fade ins and fade outs
Equalization
Time Stretching Digital Signal processing
Reversing Sounds
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Editing Digital Audio
Simple audio editing software allows: Recording of digital audio segments
Trimming
Splicing and assembly
Volume adjustments of the entire segment
Reversing Sounds Copy, cut, paste and delete segments of digital audio
Others audio editing software: COOL Edit Pro
Gold Wave
PROSONIQ SonicWORX
Samplitude Studio
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Audio formats
.WAV (Developed by IBM and Microsoft) .AU (UNIX)
.AIFF (Audio Interchange File Format)
.MP3 (MPEG layer3) .SND (Mac)
.RA (RealAudio)
.WMA (Windows Media Audio)
.VOC (SoundBlaster)
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MIDI (Musical Instrument Digital
Interface)
MIDI is a standard for specifying a musical performance
It allows different electronic devices to communicatetogether Rather than send raw digital audio, it sendsinstructions to musical instruments telling them what
note to play, at what volume, using what sound, etc.
The synthesiser that receives the MIDI events isresponsible for generating the actual sounds. Example:Keyboard Piano
MIDI data is not digitized sound: it is a shorthandrepresentation of music stored in numeric form
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MIDI Setup
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MIDI sequencers
A MIDIsequencer
allows
musicians to
edit and create
musical
compositions
like a word
processor
Cut and paste Insert / delete
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Advantages of MIDI
MIDI files are compact; the size of the file is completelyindependent of playback quality
In some cases MIDI may sound better than digital audio(if the MIDI sound source is of high quality)
MIDI data is completely editable: you can change thelength of a MIDI file by varying its tempo withoutchanging the pitch
Still used a lot in studio environment to connectsynthesizers and other equipment
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Disadvantages of MIDI
MIDI does not represent sound but musicalinstruments, so playback is very rarely accurate(usually same score, wrong instrument)
MIDI cannot easily be used to play spokendialog
An old format, people have already begun
forgetting it
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MIDI Versus Wav
Quality recording, MIDI depend to the tools
Audio .wav easier to create compare than MIDI
MIDI Advantages File Size small
Size Storage also small
MIDI Advantages Playback
Cost and Skill
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How audio can be used effectively
Examples of uses of audio: Cautions and warnings
It is a good medium for alerting users to criticalinformation. Some uses include:
Sounding an alarm when a limit is reached Alerting users when data is entered incorrectly
Music and Sound Effects These make multimedia interaction more real.
Some uses include: Musical background for a video segment
Birds Songs accompanying photographs in biologicalfield training
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How audio can be used effectively
Sound-related data. Some uses include:
Helping mechanics diagnose engine trouble
Training medical students to recognize different
breathing sounds
Direct voice communication.
Some uses include:
Leaving a voice message for other users of an
application
Consulting with an expert during a troubleshooting
procedure.
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Advantages and Disadvantages
of using audio
Sound adds life to any multimedia applicationand plays important role in effective marketingpresentations
Advantages Ensure important information is noticed
Add interest
Can communicate more directly than other media
Disadvantages Easily overused Requires special equipment for quality production
Not as memorable as visual media
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Adding Sound to Multimedia
Project
Decide what kind of sound is needed and whereyoull use them
Decide when to use midi and when to use digitalaudio
Acquire source material
Edit the sounds to fit your project
Test the sounds to be sure they are timedproperly