Sound physics

AUDIOAUDIO1. Basic physics of Sound

2. Types of Sound

3. Reception: Modes of Listening

4. Sound Art5. Recorded sound6. Audio Examples

What is sound?

• It is basically a pattern formed in the vibration or movement of molecules of air.

• It is basically a pattern formed in the vibration or movement of molecules of air.

• When a sound is made, air molecules move out from the source in waves

What is sound?

• When a sound is made, air molecules move in waves

• The waves radiate out 360 degrees and in 3 dimensions from the source until it dissipates

• When a sound is made, air molecules move in waves

• The waves radiate out 360 degrees from the source until it dissipates

• Analogous to a drop of water in a pool

• Sound is intentional vs. noise which is unwanted or unintentional

In very general terms, a sound wave has two important characteristics:

»Intensity

»Pitch

INTENSITY

• Intensity = wave amplitude = volume = loudness

• This is a measurement of the height of the sound wave

• Measured in decibels = dB

• The human ear responds to a great range of sound intensities from 0dB (threshold of hearing) to 135dB (the threshold of pain)

• VU meter in sound production is a volume unit measure

Typical Sound Levels

• Jet aircraft taking off………..…..125 dB

• Rock concert……………………120 dB

• Heavy traffic……………………. 90 dB

• Interior of a car @ 40mph………. 80 dB

• Normal conversation……………. 60 dB

• Broadcast studio………………… 20 dB

PITCH

• = Frequency

• Refers to the characteristic of the sound

PITCH

• = Frequency • Refers to the characteristic of the

sound • For example we talk about women’s

voices being a higher pitch than a man’s voice or a violin is higher pitched than a cello

PITCH

It is NOT a difference in loudness (amplitude) but of tonal quality

PITCH

• It is NOT a difference in loudness (amplitude) but of tonal quality

• Pitch refers to how often the wave repeats itself in one second.

• Each complete pattern of the wave is called a cycle

PITCH

• Measured in the number of cycles per second = Hz

• The lower the number the deeper or more bass the sound

• a frequency of 20 Hz would sound like a very low note on a pipe organ - almost a rumble

• 20 - 20000 Hz covers most audible frequencies

Temporal Terms• a sound or sound event has a structure

and a temporality


and a temporality

• the initiation of the sound is called the attack


and a temporality


• this is followed by a sustain: How long is it held? How long is it at full volume?


and a temporality


• this is followed by a sustain: how long is it held? How long is it at full volume?

• finally the sound fades away = decay

Temporal Terms• These 3 stages are parts of the

sound envelope and apply to any and all sounds

Canadian composer, artist R. Murray Schafer

In his book Voices of Tyranny: Temples of Silence, 1993 is an essay called “I’ve never seen a sound” with some wonderful thoughts:

No sound can be repeated exactly Not even your own name. Every time it is pronounced it will be different. And a sound heard once is not the same as a sound heard twice, nor is a sound heard before the same as a sound heard after.

Every sound commits suicide and never returns. Musicians know this. No musical phrase can be repeated exactly the same way twice.

Sounds cannot be known the way sights can be known. Seeing is analytical and reflective. It places things side by side and compares them (scenes, slides, diagrams…). This is why Aristotle preferred sight as “the principle source of knowledge”.

There is no silence for the living.

We have no earlids.

We are condemned to listen.

Everything in this world has its sound - even silent objects. We get to know silent objects by striking them. The ice is thin, the box is empty, the wall is hollow.

Here is a paradox: two things touch but only one sound is produced. A ball hits a wall, a drumstick strikes a drum, a bow scrapes a string. Two objects: one sound.

Types of Sound in Film3 main types of sound

– voice

– sound effects

– music

- Voice -

- dialogue

- interview

- narration

- voice over

- Sound Effects -• add realism to a scene

- synchronous: sound matches what we see (ie. someone playing the piano, the sounds of a piano are heard)

- Sound Effects - - synchronous: sound matches what we see (ie. Someone playing the piano, the sounds of a piano are heard)

- asynchronous: we don’t see the source of the sound (ie. the sound of an ambulance is used as background sound while the image portrays an arguing couple)

- Sound Effects -Ambience & Presence

• Ambience is usually the background sounds available in the environment

• can be recorded in the original production

• or it can be recorded separately and deliberately added to the sound track to provide acoustic space around the rest of the dialogue

Presence

• a location’s “aural fingerprint” = nonspecific sounds on the upper end (around 2,000 - 8,000 Hz)

Presence

• a location’s “aural fingerprint” = nonspecific sounds on the upper end (around 2,000 - 8,000 Hz)

• each room has a distinct presence of subtle sounds

Presence

• provides a continuous sounding background

• may smooth pauses in dialogue and give the feeling of life in a deadened studio recording

>> otherwise we would perceive there to be a failure of the sound system

- Music -

• background music adds emotion and rhythm

- Music -


• not meant to be noticeable

- Music -



• provides a tone or emotional attitude toward the story and/or the characters depicted

- Music -



• provides a tone or emotional attitude toward the story and/or the characters depicted

• could foreshadow an event, an approaching menace, etc.

- Music -

• background music adds emotion and rhythm• not meant to be noticeable• provides a tone or emotional attitude toward the

story and/or the characters depicted• could foreshadow an event, an approaching

menace, etc.• can be used to links scenes (ie. a motif for a

particular character)

French sound theorist

Michel Chion has described

3 Modes of Listening

• CAUSAL

• SEMANTIC

• REDUCED

- CAUSAL -

• the most common form consists of listening to a sound in order to gather information about its cause (or source)

• the source can be visible or invisible with similar effects on us

• think of a phone ringing…it can be in the scene or “off screen”

- CAUSAL -

• can also be more ambiguous in that what we recognize is only the general nature of the sound’s cause

• for instance we may (unconsciously) tell ourselves “that must be a mechanical sound” or “that must be some human”, etc.

- SEMANTIC LISTENING -

• refers to a code or a language to interpret a message: spoken language as well as other kinds of codes

• it is something we interpret in aid of the narrative

• a spoken word is not abstract…it has a linguistic meaning regardless of tone or accent

- REDUCED LISTENING -

• a mode of listening that focuses on the traits of the sound itself, independent of its cause or its meaning


• a mode of listening that focuses on the traits of the sound itself, independent of its cause or its meaning

• it takes the sound -- verbal, musical, sound effects or whatever -- as itself the object to be observed instead of as a vehicle for something else


• The descriptive inventory of a sound can’t be understood in one listening

• - often used for ambience or presence or more unconscious effects

• - very important in relation to “Sound Art”

Sound Art• Made by artists whose materials

include physical media, sound, and environments.

Sound Art

• Sound artists tend to be poorly represented by the modes of discourse that seem satisfactory for "pure" musical or visual art

• They are poorly represented by the forms of presentation available

• There are an infinite number of concerns, methods, styles and approaches

• Some sound artists work with their sound physically, allowing the physical contact with materials to influence their choices. Their work is a dialogue between the creation of physical objects and the sound generated by those objects.

• Because sound art falls between musical and visual realms, approaches to the materials can incorporate what the artist desires from either tradition

• For example Robert Racine’s Sound Signatures that uses the recording of the sound of 22 signatures

• Johan Goedhart has created installations using large amounts of computer printers continuously printing.

• In addition to spitting out reams of paper which was eventually fed back through the printers, the sounds generated were processed and made audible again through various media.

• The choice of documents to be printed in such an installation then becomes a compromise between the visual and audible output from the printers.

• The sound is a direct result of the artist's choice of physical materials.

• While others are interested in responding to mediated sound events through appropriation, sampling, re-recording and digital modification of those events

• For instance the work of V. Michael (aka The Spacewurm) uses modified police scanners, intercepts cell and cordless phone calls and digital messaging systems

• Or Fred Szymanski whose sources for Feeder #8 are computer-generated cycles of feedback sounds from computers themselves…spinning hard-drives, etc.

• Others are interested in using language to break down semantic listening modes or to build on them

• Such as dub poet Pamela Z’s Geekspeak

• Or highly conceptual works like Brandon LaBelle’s use of Roland Bathes writing in Topophony of the Text

Sound Art & Space

• Sound artists attempt to create environments as a sculptor might, but which are animated with sound. Some of them create sound sources which highlight architectural features, some deal with concepts of room acoustics.

• In addition to altering aspects of physical spaces which we inhabit, some sound artists present sounds from foreign spaces where we have never been

• these may be imaginary, created spaces or spaces inside objects and bodies.

• Alvin Lucier's Music for Solo Performer amplifies brain waves

• John Cage and David Tudor amplified a variety of internal sounds from plants and machines

• Richard Lerman also has created a large body of work dealing with internal sounds of unexpected objects, like bridges, plants

• They are exploring and exploding concepts of the transmission of sound through different media

Remember...• That sound is a spatial and temporal event

• Techniques of recording, reproduction, intervention and even the mode of output, will all impact its spatial and sonic qualities.

• Try to capitalize on this in your project

Remember...

• ...that sound often has not just one, pure source but at least two...three... and even more.

Remember...

• ...that sound often has not just one, pure source but at least two...three... and even more.

• for instance as I am typing these notes, there is the sound of my fingers on the keys,

Remember...

• ...that sound often has not just one, pure source but at least two...three... and even more

• for instance as I am typing these notes, there is the sound of my fingers on the keys, my watch hitting the table

Remember...

• ...that sound often has not just one, pure source but at least two...three... and even more

• for instance as I am typing these notes, there is the sound of my fingers on the keys, my watch hitting the table, my breathing

Remember...• ...that sound often has not just one, pure

source but at least two...three... and even more

• for instance as I am typing these notes, there is the sound of my fingers on the keys, my watch hitting the table, my breathing and incidental sounds such as the ventilation, the clock ticking and so on

MICROPHONE BASICS

• there are different types of microphones, but they all do the same thing

• they transform acoustical movements (the vibrations of air created by the sound waves) into electrical vibrations. This conversion is relatively direct and the electrical vibration can then be amplified, recorded, or transmitted.

TYPES• Deciding on kind of microphone to use

depends on what you want and where you are recording

• Omni will pick up sound 360 degrees around it therefore doesn’t emphasize any one direction or location

• Cardiod will not pick up very much sound from behind it. Used for concerts, speeches, lapel mic

• Shotgun microphone will pick up the voices of the talent with a comfortable amount of the surrounding ambient sound. Unlike the sterile, close mic'd sound that is typical with a lavaliere microphone, the shotgun mic usually exhibits a fuller, richer and more pleasing sound quality.

REALISM?

• Live sound is very different than recorded sound

• In real life we are marvelously able to cut out (from our hearing) any extraneous sounds and focus on single sounds…

REALISM?

• Live sound is very different than recorded sound

• In real life we are marvelously able to cut out (from our hearing) any extraneous sounds and focus on single sounds…

• Imagine a noisy party in which you are having a conversation with one person…

REALISM?

• This process of selective listening is actually known as the Cocktail Party Effect

REALISM?


• This becomes very difficult to do as a listener of recorded material… that’s where audio editing comes in…

REALISM?


• This becomes very difficult to do as a listener of recorded material… that’s where audio editing comes in…you must mimic how we hear and that requires re-creating or reconstructing HOW we hear.

Sound & Image

• They have a very complex inter-relationship

• They are BOTH illusions constructed within a system of production

• We all participate in an audio-visual contract -- one we learn in order to watch films, videos, TV…

VALUE ADDED

• Is one of the most important relationships in the audio-visual contract between sound and moving image

VALUE ADDED

• Michel Chion states that Value Added is:

“the expressive and informative value with which a sound enriches a given image

VALUE ADDED


“the expressive and informative value with which a sound enriches a given image so as to create the definite impression, in the immediate or remembered experience one has of it,

VALUE ADDED


“the expressive and informative value with which a sound enriches a given image so as to create the definite impression, in the immediate or remembered experience one has of it, that this information or expression “naturally” springs from what is seen.

VALUE ADDED

• Gives the (eminently incorrect) impression that sound is:

• 1) unnecessary

• 2) merely duplicating a meaning which in reality it brings about, either all on its own or by discrepancies between it and the image

• Ingmar Bergman’s Persona (1966)• We’ll watch the opening sequence twice.

The first time with sound, the second time with no sound.

• Make note of the differences in how you perceive the images with and without sound.

Resources www.filmsound.org www.ubu.comMichel Chion “Audio-Vision”

Sound physics

Education

Transcript of Sound physics