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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If the crest and valleyof two waveforms are

perfectly out of phase,they cancel each otherresulting in no waveformat all.


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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

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Analog and Digital SoundHistory

Evolution from analog to digital technology. The analog century begins with a nursery rhyme.

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http://localhost/var/Books/Digital_Audio_Book


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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.



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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.



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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



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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.



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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



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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.



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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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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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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 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.

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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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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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www.soundrangers.com

Sound Design


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www.partnersinrhyme.com

Sound Design


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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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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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