FY Seminar Acoustics

7/22/2019 FY Seminar Acoustics

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First Year Seminars:Music and the Mind

&

Music Mediated

The Acoustics of Music


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Music AcousticsI suspect that many people share the

romantic sense that music is a product ofnuminous inspiration, and are apt to feeldisheartened, even appalled, when it isfragmented and seemingly reduced to a matter of

mere acoustics, of the physics and biology ofsound and audition. I don t intend to apologize for a digressioninto the mathematics, physics and physiology of

acoustic science by justifying it as an unavoidableintroduction to the raw materials of music.It is much more interesting than that.

~ Philip Ball


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What is SOUND?


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Sound

If a tree were to fall on anuninhabited island,and no one were around to hearit,

would it make a sound?


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Sound: Definitions

A DISTURBANCE OF AIRMOLECULES THAT IMPINGES UPONTHE EARDRUM .

Scientific def: Sound = Compressionand rearefaction within a medium.

What

s a medium?


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Sound WavesSound travels as a wave.Sound Waves can: carry a little energy or a lot. be short or long. travel fast or slow.

All waves (Sound, light, X-ray), share basiccharacteristics:

1. amplitude2. wavelength3. frequency


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Sound travels as a wave:Compression

Decompression, expansion orrarefaction


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Sound WavesBasic characteristics: Amplitude: The higher the wave moves

up-and-down as it vibrates,

the larger the amplitude of the resultingwaves.


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Sound WavesBasic characteristics: Wavelength: Def.: The distance

between two consecutive crests ortroughs of a wave.

The wavelength can be measured frompoint to point.


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Sound Waves Wavelength:

short wavelengths = High Frequencies

long wavelengths = Low Frequencies


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Sound WavesBasic characteristics: Frequency: Def.: Number of complete waves,

or complete cycles, per unit of time. Frequency is measured in hertz (Hz). Hz = # of Vibrations per second.


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Sound waves: musical

? Music = what kind of sound waves? ? Noise = what kind of sound waves?

The factor that makes the differencebetween

music

and

noise

is called: _______________ ?


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? Music = what kind of sound waves? Regular/Repeating

? Noise = what kind of sound waves?Irregular

The factor that makes the differencebetween

music

and

noise

is called: periodicity


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Periodic i ty is the factor whichmakes the difference between

~ one ~vs

Noise


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High Pitch/short wavelength: travel in STRAIGHT LINES will hit an obstacle ( e.g. wall ) and be reflected in another

direction (bounce back); reflect ion (physics)


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Low pitch/long wavelength: will BEND when hitting an obstacle

and keep going; refract ion


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4 Properties of Musical TONE Scientific Term Definition Objective Term

Frequency # of cycles persecond,measured inHertz (Hz)

Pitch

Amplitude Intensity Loudness

SpectralEnvelope

Timbre Quality; Tonecolor

Duration Length Time


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Spectral Envelope/Timbre

Musical Sound, a.k.a

tone

: Complexper iodic v ibra tions

The lowest, slowest and strongest frequency:

Fundamental: F 0

Frequencies over F 0: Overtones, Harmonics* *preferred term


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Harmonics


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Harmonics

Harmonics : Frequencies which occur at wholenumber multiples* of the Fundamental (F 0); ex.: x1, x2, x3, etc.term: Consonance(con = with ; - sonance = sonar/sound) Partials: frequencies which occur above F 0 butNOT at Whole number multiples* of the F 0.term: DissonanceDis- against; - sonance = sonar/sound


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Overtones: 2 types

Harmonics Whole numbermultiples of the F 0

Part ialsNot Whole numbermultiples of the F 0 Interfere withsound, createroughness Noise


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Harmonics

Harmonics are what give anymusical instrument its particulart imbre.

Timbre is an identifier: a

sonicfingerprint,

unique to each instrument.


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Harmonics

Every musical intrument has someharmonics which are: Emphasized- boosted -

louder

and Reduced attenuated -

softer

This sonic

fingerprint

is called: spec t ra lenvelope


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Clarinet A 440


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Flute G 4


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Human Voice (Singing)


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Harmonics

Harmonics are: Frequencies whichoccur at whole number multiples* ofthe F 0; ex.: x1, x2, x3, etc.This series of Frequencies is called theHarmonic Series.

Example: Low C = 130 Hz, where (atwhat frequency) should the harmonicsoccur?


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Harmonic SeriesC 3 = 130 (F 0 and H 1 are the same)2nd H = C 4 = Hz?3rd H = G 4 = Hz? 4th H = C 5 (

middle C

) = Hz?5th H = E 5 = Hz?


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Harmonic SeriesC3 = 130 (F 0 and H 1 are the same)2nd H = C 4 = 261 Hz 3rd H = G 4 = 392 Hz 4th H = C 5 (

middle C

) = 523 Hz5th H = E

5= 659 Hz and so on


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Harmonics: 2 types

Harmonics Whole numbermultiples of the F 0

Part ialsNot Whole numbermultiples of the F 0;

Other

Interfere withsound, createroughness Noise


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Harmonics:

Take-Home MessageThe more HARMONICS in the tone, the more:

Musical, pleasing, in

tune IT SEEMS.The more partials in the tone, the more noisy, alarming(exciting!), out-of-tune it SEEMS.


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Terms

ConsonanceDissonance


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Equal Temperament

The tuning system used in modern,Western music, in a 12 tone scale:

Based on pure, mathematical ratios ofonly the octave and 5th intervalsbut not for the other intervals (2nd, 3rd,

4th, 6h and 7th)


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Harmonics

The Amplitude of Harmonics often (notalways) diminish in frequency (Hz) as theygo higher

??: What does this mean re:

loudness

of harmonics?


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The Ampli tude of Harmonics diminishin frequency (Hz) as they go higher


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Coupled Acoustics

1. Musical Instruments/3 Elements in Common

2. Actuator3. Vibrator 4. Resonater


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3 Elements: VOICE

1. Actuator: AIR

2. Vibrator: VOCAL FOLDS3. Resonater: LARYNX, PHARYNX ,

AND ORAL CAVITYLaryngeal, pharyngeal, oral (or

buccal

)


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3 Elements : Violin

1. Actuator: bow

2. Vibrator: string3. Resonater: body


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3 Elements : Piano

1. Actuator: hammer (finger)

2. Vibrator: string3. Resonater: body


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3 Elements : Clarinet

1. Actuator: air (lips)

2. Vibrator: reed3. Resonater: body


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3 Elements : Trombone

1. Actuator: lips

2. Vibrator: lips3. Resonater: body


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Resonance: Definitions

The amplification, reinforcement, or prolongation of vibration when anothervibration of the same frequency isapplied to it. Text: page 72)Merriam-Webster Dictionary:

theintensification and enriching of amusical tone by supplementary

vibration

(see also Glossary in Text)


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Resonance: 2 Types

1. Forced (ak.a. conductive ) Depends upon direct, mechanical connection ofactuator to vibrator

2. Free (a.k.a. sympathetic)Depends upon reflections of soundwaves within avoid3 conditions:

1. Structure must be hollow2. Have enough space3. Have an opening for exit of soundwaves


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Resonance Clarification: 3 main resonators:

1. Pharynx

2. Larynx

3. Oralcavity

(not

mouth

)


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Resonance: factors

3 factors affect resonance:1. Size2. Shape3. Texture

These factors affect all 4 properties of musicaltone* (Some more than others).

(REVIEW: WHAT ARE THE 4 PROPERTIESOF A MUSICAL TONE?)


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4 Properties of Musical TONEScientific Term Definition Objective Term

Frequency # of cycles persecond,measured inHertz (Hz)

Pitch

Amplitude Intensity Loudness

SpectralEnvelope

Timbre Quality; Tonecolor

Duration Length Time


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Resonance: 3 factors1. Size

Affects Frequency & timbre; how/why?Voice: How might this relate to gender?


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Shape

Affects Frequency &timbre how/why?


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Affects on Resonance of:Texture?


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Venues


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Pavarobotti

Documents

FY Seminar Acoustics