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Basic of Sound
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IMD20503 Digital Audio and Video
Basic of SoundHow sound works
Analog and digital sound technology
Sound design
Notes can be downloaded from \\10.36.1.174
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How sound worksImportance of sound
Sound is essential in communicating knowledge. Sound greatly enhances images and, especially, video or
animation.
Sound can manipulate the mood of spectators with
background music and sound effects.
Sound can provide continuity to jumpy frame cuts, but
audiences react gingerly to out-of synch dialog and
misplaced sound effects. Enhanced MM in the form of voice-overs, narrations and
instructions.
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How sound worksWhat is sound?
Sound is basically a vibration. (analog) Sound is a force:emotional, perceptual, physical.
It can excite feeling and convey meaning
Sound is omnidirectional
everywhere. When something makes a sound, it vibrates and emits
pressure waves that are received in the human ear. The
brain interprets these as sound.
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How sound worksWaveform / Sound wave
A waveform or sound wave gives us a measurement of the
speed of the air particles and the distance, which theytravel for a given sound.
Period is the distance between two crests, and measured
in seconds.
A number of crests (peaks) may occur within a second, so
the number of peaks that occur in one second is called the
frequency.
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How sound worksComponents of waveform
Acronym : WAVE PFH Wavelength
Amplitude
Velocity Envelope
Phasing
Frequency
Harmonics
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How sound worksWavelength/ Cycle
Describes a single repeated sequence of pressure changes
from zero pressure to high pressure to low pressure and backto zero.
Literally, the length of the wave.
The length of a wave is measured from one point on the
waveform to the exact point of the next repeating cycle. The physical distance through a medium such as atmosphere,
that a soundwave travels to complete cycle.
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How sound worksWavelength/ Cycle
A
A = wavelength
B = degree of phase
0O
90O
180O
270O
360OB
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How sound worksAmplitude
The amplitude measures the relative loudness of the
sound, which is the distance between a valley and a crest.
The amplitude determines the sounds volume.
High amplitude waveforms are loud and low amplitude
waveforms are quiet. The volume of sound or amplitude is measured in decibels
(dB).
A decibel is the smallest change in loudness that a human
ear can detect. Human hearing ranges from 1 decibel, called the threshold
of hearing, to over 120 decibels, the threshold of pain.
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How sound worksAmplitude
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How sound worksVelocity
Speed through the atmosphere. The speed or velocity in air and other gases depends on
temperature.
Speed of sound increase in warm, moist air and decrease
in cold, dry air.
Sounds at high amplitude might go father but travel slower
which is the opposite for lower amplitude.
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How sound worksEnvelope
Refers to an imaginary curve that wraps the entire waveform,
generated by musical instruments All sound posses a characteristic change in amplitude or
loudness as time increases.
The features included in an envelope are attack, decay, sustainand release(ADSR).
i. Attack The sudden increase of amplitude to full sound intensity.
ii. Decay
occurs just after the attack, is a slight decrease in amplitude.
iii. Sustain
the main part of a note, when it plays for its longest duration or thesound is held.
iv. Release
which the amplitude fades out (when lifting a finger from a key).
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How sound worksEnvelope
Attack Sustain Release
A
m
p
li
t
ud
e
Decay
Duration
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How sound worksPhasing
Think of phase as the information our ears use to tell from
where a sound originated, because sound arrives at our
ears at slightly different times.
measured in degrees (0-360), indicates the position of a
waveform in a cycle. 0o is the start point, 90o at high pressure, 180o at halfway
point, 270o at low pressure and 360o is the end point
Types of phase :
In phase
Out of phase
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How sound worksPhase
If the crest and valley areperfectly in phase, they
reinforce each otherresulting in a waveform, thathas higher amplitude thaneither individual waveform.
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How sound worksPhase
If the crest and valleyof two waveforms are
perfectly out of phase,they cancel each otherresulting in no waveformat all.
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How sound worksPhase
Sound waves whichhave varying phaserelationships producea more complexwaveform. A complexwaveform thatrepresents music,voice, noise and othersounds.
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How sound worksFrequency and Pitch
Frequency is the number of cycles that a vibration completes in
one second. Measured in hertz (hz) for example a 1000 hz waveforms is
1000 cycles per second.
As an object oscillates more rapidly, it creates a high pitchsound, which is registered as a high frequency sound.
The higher the frequency, the higher the pitch.
A low-frequency sound is produced by a slowly vibrating object,such as the thicker strings on a guitar.
Pitch is measured by frequency.
Pitch is the relative tonal highness or lowness of a sound.
The human ear can perceive a range of frequencies from 20 Hz(Hertz) to 20,000 Hz (Also expressed as 20 KHz).
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How sound worksFrequency and Pitch
Comparison of frequency range
Name Low frequency High frequency
Human 20 Hz 20,000 Hz
Cat 45 Hz 85,000 Hz
Dog 50 Hz 45, 000 Hz
Elephant 5 Hz 10,000 Hz
Bat 10,000 Hz 120,000 HzDolphin 1,000 Hz 120,000 Hz
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How sound worksOthers
Few objects produce sounds at a single frequency. Mostmusical instruments generate multiple frequencies for every
note, so that the difference between two same-pitch
instruments can be noted, e.g. a violin and a flute or a piano
and a bass.
The combinations of frequencies in an instrument is known as
the timbre.
A sound wave has a main frequency and minor frequencies,
referred as overtones orharmonics.
Duration measures frequency, amplitude and timbre over time.
Fourier TheoremA sound wave is a combination of sinus
waves created during vibration.
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How sound worksComplex sound wave
A complex sound wave showing a main
frequency and minor overtones.
Minor frequency
Major frequency
A l d Di it l S d
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Analog and Digital SoundHistory
Evolution from analog to digital technology. The analog century begins with a nursery rhyme.
A l d Di it l S d
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Analog and Digital Sound
In analog and digital audio, sound is transmitted andstored in very different ways.
Analog audio using positive and negative voltage
Digital audio using zeros (0) and ones (1)
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Analog and Digital SoundAnalog sound
Analog means the same as or similar to. Root words analogous and analogy, both of which
mean a similar copy.
Analog signals are exact replicas of the original sound
source. Noise exist in the recording ( not the sound source but part
of the analog recording).
Analog media :
Audio cassette LP record
Reel-to-reel tape
Broadcast television
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Analog and Digital SoundAnalog soundanalog media
Audio Cassette
LP record / Vinyl
Reel-to-reel tape
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Analog and Digital SoundDigital sound
Digital means numbered. Using number is often a more precise way of expressing
information.
The conversion of analog signals into a form that a
computer can breakdown.
Digital media :
Compact Disc
DAT MiniDisc
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Analog and Digital SoundDigital sounddigital media
Compact Disc
Digital Audio Tape (DAT)
MiniDisc
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Analog and Digital SoundHow digital recording works?
Audio becomes digital audio when it passes from ananalog source, such as microphone or audio out of a
keyboard to you PC.
Analog and Digital So nd
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Analog and Digital SoundHow digital recording works?
The recording process of a digital system takes samples ofthe analog signals as it enters the system.
In order to get good digital recording, it has to have
enough :
Samples per second
Bit depth to accurately reproduce the source material
Audio CD quality uses 44,100hz, stereo and 16 bit
samples per second.
Analog and Digital Sound
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Analog and Digital SoundSample rate
Sample rate indicates the number of digital samples takenof an audio signal each second.
This rate determines the frequency range of an audio file.
The higher the sample rate, the closer the shape of the
digital waveform to the original analog waveform.
Low sample rates limit the range of frequencies that can
be recorded which can result in a poor recording.
To reproduce a given frequency, the sample rate must beat least twice that frequency.
Analog and Digital Sound
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Analog and Digital SoundSample rate
Sample rate Quality level Frequency range11,025 Hz Poor AM radio (low end
multimedia)
0 5,512 Hz
22,050 Hz New FM radio (high end
multimedia)
0 11,025 Hz
32,000 Hz Better than FM radio (standard
broadcast rate)
0 16,000 Hz
44,100 Hz CD 0 22,050 Hz
48,000 Hz Standard DVD 0 24,000 Hz96,000 Hz High-end DVD 0 48,000 Hz
Analog and Digital Sound
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Analog and Digital SoundBit depth
Bit depth determines dynamic range. When a sound wave is sampled, each sample is assigned
the amplitude value closest to the original waves
amplitude.
Higher bit depth provides more possible amplitude values,producing greater dynamic range.
Analog and Digital Sound
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Analog and Digital SoundBit depth
Bit depth Quality level Amplitude values Dynamic range
8 bit Telephony 256 48 dB
16 bit CD 65,536 96 dB
24 bit DVD 16,777,216 144 dB
32 bit Best 4,294,967,296 192 dB
Analog and Digital Sound
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Analog and Digital SoundAnalog vs digital
Which is better?
There are differences between analog and digital butneither is better or worse than the other.
They are simply different.
But now our focus is on digital audio because :
We will use digital audio most of the time throughsoftware and hardware to create, record and processthe sound work.
The start up expenses are relatively low compared with
purchasing analog gear.Analog systems (recording and editing) are becoming
obsolete.
Analog and Digital Sound
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Analog and Digital SoundAnalog vs digital
Today, every sound designer works in the digital arena. Many professional music recordings in the studio are
recorded on tape.
Usually this recording is digitized, processes and edited in
a Digital Audio Workstation (DAW) and then sent back totape or storage medium like a hard drive.
Both the analog and digital processes are at work but this
is changing.
Sound Design
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Sound DesignWhat is sound design?
What is sound design?
How important it is to a visual and nonvisual experience?
Where does it all begins?
Sound design is a technical/conceptually creative field.
Sound Design can also be defined as: "The manipulationof audio elements to achieve a desired effect."
It covers all non-compositional elements of a film, a play, a
music performance or recording, computer game software
or any other multimedia project.
A person who practices the art of sound design is known
as a Sound Designer.
Sound Design
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Sound DesignWhat is sound design?
Area that uses sound designer :
1. Theatre Use large mechanical devices to produce sound
effects.
Now, there are 2 roles of sound design in theatre :
Technical Sound Design Design sound system
Conceptual Sound Design
Design what sound to be used to create mood
and setting of the play.2. Radio
Use large mechanical devices then better technologyallows sound effects to be recorded and library ofsound was created.
Sound Design
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Sound DesignWhat is sound design?
3. Film
Originally the sound effects was recorded live asthe film was being projected onto a large screen ina recording studio.
Now, sound effects track is complied of many
tracks layered together and mixed to form adynamic soundtrack.
Foley sound effects create sound effects in thestudio by Foley artists.
4. Music Involved in the creation of the overall sound of a
recording and sometimes live performance.
Sound Design
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Sound DesignWhat is sound design?
Sound Design
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Sound DesignSound effects design in Star Wars
Name Effects
R2D2 Half of the sound are electronic and the other half are
vocalization, water pipes and whistles
Imperial walkers A machinists punch press along with the sounds of bicycle
chains dropping on cement.
Light saber An old tv set along with the hum of a 35mm projecter mixed
together.
Laser blasts A hammer hitting the wires of a radio tower.
Sound Design
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Sound DesignSound effects design in Star Wars
Name Effects
Tiefighter An elephants bellow altered in various way.Speeder bike A P-5 Mustang airplane and a P-38 Lockheed Interceptor
combined and mixed.
Luke Skywalkers
landspeeder
The sound of Los Angeles Harbor Freeway through a vacuum
cleaner pipe.
Chewbacca The sounds of walruses and other animals combined together.
Ewokese
language
The combination and layering Tibetan, Mongolian and Nepali
languages.
Sound Design
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Sound DesignStages in sound design
1. Pre production
Story, design document, proposal Spot for sound effects
Defining sound effects and sources
Sound blueprint and approval process
Technical playback considerations
2. Production
Sound asset collection
Inventing original sound3. Post production
Sound processing
Sound Design
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Sound DesignPre production
Story, design document, proposal
The sound design process starts with a workingconcepts.
Can be anything from a design document to the mood
of the director or producer has in mind.
Need to get a feel for what the message is going to be
in the project.
If it is a script, the text need to be reviewed for the
sound conceptualization.
Sound Design
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Sound DesignPre production
Spot for sound effects
Spotting for sound is simply gaining some ownershipto the design document or screenplay.
It is a process of literally writing down aural ideas as the
reading occurs.
The processes include:
the first impression of the target
sketch out rough sound map with the outcome
expected from the project. Write down as many ideas as can fit on the page
because it will save many hours of planning.
Sound Design
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Sound DesignPre production
Defining sound effects and sources
Details on what the sound are and where they are to befound such as at sound libraries and live recording.
Sound designer need to be familiar with sound libraries
and recording techniques.
There are also many online sites that have free
downloadable sounds and fee-based sound for usage
and collection not of high quality sound.
A good tips is to start collecting sound your own soundlibrary even if you do not need them in projects because
we can use them in future works.
Sound Design
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Sound DesignPre production
www.soundrangers.com
Sound Design
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Sound DesignPre production
www.partnersinrhyme.com
Sound Design
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Sound DesignPre production
Sound blueprint and approval process
Need to get approval for the work.
Categorize the sound based on frequency ranges,
types of sound used and any other characteristic that
can be defined.
Sound Design
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Sound DesignPre production
Technical playback considerations
When creating the initial plan for the sound design,consider :
What the playback device will be?
What platforms? If it is for the Internet, the bandwidth and the average
playback system need to be decided.
Compression formats
In film, need to consider theater or cinema standardsie Dolby, THX, DTS
Sound Design
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Sound DesignProduction
Sound asset collection
Start collecting the sound asset based on the pre-production stage.
The sounds can be from sound libraries or source
recordings.
Sound object falls into two types:
Single sound
Mixed sounds
Sound Design
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Sound DesignProduction
Inventing original sound
Originally recorded sounds are better, more fitting for thescenario and more original.
2 types of sound effects:
Small subject sounds
Glasses clinking, paper being crumpled, doorsqueaks, footsteps, cloth movement and humannoises (sneezing, coughing).
Recorded in a studio or by Foley artists.
Big subject sounds
Sounds that need to be recorded outside such asexplosion, gunfire, crowds, cars, planes, trains andmachinery.
Sound Design
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Sound DesignPost Production
Sound processing
Altering and enhancing sounds to fit the scenario.
The final stage is mixing and mastering the sound objects.
In film, the re-recording process integrates all of the
elements together and mixes them into a composite
soundtrack.
Soundtrack consists of the dialogue track, music track and
sound effects track.
The three entities need to be properly mixed and placed in
order to be effective.
The soundtrack should support the visual content and
storyline.
Summary
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Summary
How sound works Definition
Terms : WAVE PFH
Analog and digital sound technology
Analog vs digital
Sound design
Definition
Stages in sound design; pre production, production andpost production.
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