SoundPertemuan 11 & 12

Matakuliah : O0414 - Computer / MultimediaTahun : Feb - 2010

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu :• Menerapkan 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 air pressure

• Sound comprises the spoken word, voices, music and even noise.

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Sound• As the sound vibrates it

bumps into molecules of the surrounding 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

distancealong wave

Cycle

Time for one cycle

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The characteristics of sound waves

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The characteristics of sound waves

• 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– Sound’s intensity or loudness– The louder the sound, the larger amplitude.

• In addition, all sounds have a duration and successive musical sounds is called rhythm

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The characteristics of sound waves

distancealong wave

Cycle

Time for one cycleAmplitude

pitch

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Example waveforms

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Capture and playback of digital audioAir pressure

variations

Captured viamicrophone

Air pressurevariations

ADC

Signal isconverted into

binary(discrete form)01010011010110101111

Analogueto DigitalConverter

DACConverts back 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

• When you present the sound wave as numbers, the process is called digitizing and the result will become digital audio

Digitized Sound

• Is a sampled sound.• Every nth fraction of a second, a sample of sound is

taken and stored as digital information

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01101011101101101011011011011101101111011011101101101110111101101101010100010110110110101101101001101101101101101101101010101010011001100100100110011001101001101011101101101011011011011101101111011011101101101110111101101101

01010001011

Digital Sound Quality

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Quality of digital sound depends on

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Digital sampling - Sampling Rate

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Digital sampling - Sampling Rate

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Sampling Parameters• Sampling Rate

– Measured in Hertz (Hz)– The higher sampling rate, higher quality sound

but size storage is big.– Standard Sampling rate:

• 48.000 kHz (DAT) - Digital Audio Tape, also DVD• 44.100 kHz (CD) - Compact Disk - typical quality of

most sound cards• 22.050 kHz - Medium quality, FM Radio• 11.025 kHz - Low quality (frequently used for

speech), AM Radio• Telephone?

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Sampling Parameters

• Sample size – 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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Digital audio editing software• One of the most powerful and professional PC-based software is previously

known as Cool Edit. It’s 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 sends instructions to musical instruments telling them what note to play, at what volume, using what sound, etc.

• MIDI data is not digitized sound: it is a shorthand representation 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 (if the MIDI sound source is of high quality)

• MIDI data is completely editable: you can change the length of a MIDI file by varying its tempo without changing the pitch

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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 spoken dialog

MIDI VS Wav

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How audio can be used effectively• Cautions and warnings

– It is a good medium for alerting users to critical information. 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 biological field

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 application and

plays important role in effective marketing presentations

• 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• Determine the sound playback

capabilities that the end user’s system offers

• Decide what kind of sound is needed and where you’ll 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

Exercises• Explore the View tab and Insert Sound function on

Microsoft PowerPoint 2007• Make a presentation of your favorite song, complete with

the song demo and other element which attracts you to the song

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