matakuliah tahun
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Sound
Pertemuan 6
Matakuliah : T0732 / Sistem Multimedia
Tahun : 2007
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Learning OutcomesPada akhir pertemuan ini, diharapkan mahasiswa akan
mampu :
Menunjukkan Penggunaan Suara pada AplikasiMultimedia
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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 variationsin air pressure
Sound comprises the spoken word, voices, music and evennoise.
As the sound vibrates it bumps into molecules of thesurrounding medium causing pressure waves to travel away
from the source in all 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 higher pitch of
sound
Amplitude Sounds intensity or loudness The louder the sound, the larger amplitude.
In addition, all sounds have a duration and successive musical sounds iscalled rhythm
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The characteristics of sound waves
distance
along waveCycle
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 audioAir pressure
variations
Captured via
microphone
Air pressure
variations
ADC
Signal isconverted into
binary
(discrete form)
0101001101
0110101111
Analogueto DigitalConverter
DAC
Convertsback into
voltage
Digital toAnalogueConverter
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The Analogue to Digital Converter (ADC) An ADC is a device that converts analogue signals into digital signals
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 whatit sees into a discrete value at that specific moment in time
The process to convert the analogue to digital sound is called Sampling.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 Parameters Sampling Rate Frequency of sampling Measure in Hertz
The higher sampling rate, higher quality soundbut size storage is big.
Standard Sampling rate: 48.000 kHz (DAT) - Digital Audio Tape, also DVD
44.100 kHz (CD) - Compact Disk - typical quality ofmost sound cards
22.255 kHz - Medium quality 11.025 kHz - Low quality (frequently used for
speech)
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Sampling Parameters 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 more memory (or disk storage)
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Size sample
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Quantisation Samples are usually represented the audio sample as a
integers(discrete number) or digital
1 5
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Calculating the size of digital audio The formula is as follows:
The answer will be in bytes
Where:
sampling rate is in Hz
Duration/time is in seconds
resolution is in bits (1 for 8 bits, 2 for 16 bits)
number of channels = 1 for mono, 2 for stereo, etc.
8
channelsofnumberresolutiondurationrate
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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
8
channelsofnumberresolutiondurationrate
44100 * 60 * 16 *2
8
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Digital audio editing software One of the most powerful and professional PC-based software is previously
known as Cool Edit. Its now known as Adobe Audition. Same program,
new company.
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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: Sound Forge
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 layer 3)
.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 communicate
together Rather than send raw digital audio, it sendsinstructions to musical instruments telling them what note toplay, at what volume, using what sound, etc.
The synthesiser that receives the MIDI events is responsible
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 MIDI sequencer
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 completely
independent of playback quality
In some cases MIDI may sound better than digital audio (ifthe MIDI sound source is of high quality)
MIDI data is completely editable: you can change thelength of a MIDI file by varying its tempo without changingthe 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 musical
instruments, 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 begunforgetting 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 Disadvantages Playback
Cost and Skill
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How audio can be used effectively 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. Someuses include:
Musical background for a video segment
Birds Songs accompanying photographs in biological fieldtraining
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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 breathingsounds
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 application and
plays important role in effective marketingpresentations
Advantages Ensure important information is noticed
Add interest
Can communicate more directly than other medi
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 where youll
use them
Decide when to use midi and when to use digital audio
Acquire source material
Edit the sounds to fit your project
Test the sounds to be sure they are timed properly