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Sound, Audition �& Pitch Perception

Chapter 11

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Outline

•  Function of sound

•  Definition of sound

•  Physical characteristics of sound (amplitude & frequency)

•  Audibility curve

•  Timbre

•  Structure of the ear

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If a tree falls in the forest and no one is there, does it make a sound?

•  Physical definition – pressure changes in the air or other medium

•  Perceptual definition –  experience we have when we hear

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Sound waves

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Sound waves

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/tralon.html

www.kettering.edu/~drussell/Demos/waves/wavemotion.html 11/7/11 5 11/7/11 6

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Measuring sound waves

Physical Signal Percept

Amplitude

(Change in sound pressure)

Loudness

(Perceived amount of energy)

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Amplitude

dB

Measuring sound waves

Frequency

Hz

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Perception of pitch is related to frequency

Measuring Sound Waves

The Physical Signal The Percept

Amplitude Loudness

Frequency Pitch

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Tone height - increase in pitch that happens when frequency is increased

Tone chroma – notes separated by octaves sound the same

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Range of hearing Audibility function

•  Loudness is determined by amplitude AND frequency

speech

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Audibility function

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Sound quality: Timbre

440 Hz

880 Hz

1320 Hz

Complex tone (additive synthesis)

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Frequency spectrum

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Stapes

Oval window

Round window

Malleus

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