PHY2464 -The Physical Basis of Music 1 PHY-2464 Physical Basis of Music PHY PHY- 2464 2464 Physical Basis of Music Physical Basis of Music Presentation 5 Human Ear Taken largely from Sam Matteson’s Unit 2 Sessions 12 & 13 Sam Trickey Jan. 26, 2005 Presentation 5 Presentation 5 Human Ear Human Ear Taken largely from Sam Matteson’s Unit 2 Sessions 12 & 13 Sam Trickey Jan. 26, 2005 PHY PHY- 2464 2464 Pres. 5 Human Ear Pres. 5 Human Ear Ludwig van Beethoven Ludwig van Beethoven (1770 (1770- 1827) 1827) 9th Symphony (Choral) 9th Symphony (Choral) Composed when he was Composed when he was profoundly deaf (from 1820 profoundly deaf (from 1820 onward). onward).
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PHY2464 -The Physical Basis of Music
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PHY-2464Physical Basis of Music
PHYPHY--24642464Physical Basis of MusicPhysical Basis of Music
Presentation 5Human Ear
Taken largely from Sam Matteson’s Unit 2 Sessions 12 & 13
Sam TrickeyJan. 26, 2005
Presentation 5Presentation 5Human EarHuman Ear
Taken largely from Sam Matteson’s Unit 2 Sessions 12 & 13
Sam TrickeyJan. 26, 2005
PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Ludwig van BeethovenLudwig van Beethoven(1770(1770--1827)1827)
9th Symphony (Choral)9th Symphony (Choral)Composed when he wasComposed when he wasprofoundly deaf (from 1820profoundly deaf (from 1820onward).onward).
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PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
The The earear is a highly sensitive sound receptor in which is a highly sensitive sound receptor in which •• outer ear pressure fluctuations are transformed into outer ear pressure fluctuations are transformed into •• vibrations of small bones (the vibrations of small bones (the ossiclesossicles) in the middle ) in the middle ear that ultimately are communicated toear that ultimately are communicated to•• the cochlea, in the inner ear, where the vibrations are the cochlea, in the inner ear, where the vibrations are further transformed by further transformed by stereociliastereocilia (hair cells) into (hair cells) into •• neural impulses distributed by frequency and scaled neural impulses distributed by frequency and scaled by intensity.by intensity.
PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Anatomy of EarAnatomy of Ear
Outer EarOuter Ear
Middle EarMiddle Ear
Inner EarInner Ear
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PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Outer Ear AnatomyOuter Ear AnatomyPinnaPinna –– (the feather) matches ear canal to outside (the feather) matches ear canal to outside
world. This is the ear we see. world. This is the ear we see.
MeatusMeatus –– ( the passageway) conducts sound into ( the passageway) conducts sound into head. This is the “ear canal”.head. This is the “ear canal”.
TympaniumTympanium –– (the drum) transforms (the drum) transforms pressure pressure fluctuations into displacement.fluctuations into displacement.
PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Outer EarOuter Ear
•• PinnaPinna ————→→
•• MeatusMeatus ——————→→ ←←—— TympaniumTympanium
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PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Anatomy of EarAnatomy of Ear
Middle EarMiddle Ear
PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Middle Ear Anatomy: The Middle Ear Anatomy: The OssiclesOssicles (little bones)(little bones)
MalleusMalleus (the hammer) (the hammer) -- moved by moved by TympaniumTympanium..
IncusIncus ― (the anvil) supported by ligaments that ― (the anvil) supported by ligaments that
protect against loud percussion.protect against loud percussion.
StapesStapes ― (the stirrup) force multiplied by 1.3 ― (the stirrup) force multiplied by 1.3
because of lever action.because of lever action.
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PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Frequency Discrimination in CochleaFrequency Discrimination in Cochlea•• 20 Hz to 20 kHz (typical in human beings)20 Hz to 20 kHz (typical in human beings)
•• Resonances in Basilar membrane and in Hair Resonances in Basilar membrane and in Hair Cells (HC) cause spatial separation by frequency.Cells (HC) cause spatial separation by frequency.
•• Differential movement of membranes stimulate Differential movement of membranes stimulate HC.HC.
•• Minimum stimulation required for response. Minimum stimulation required for response. Inhibition of neighbors causes nonInhibition of neighbors causes non--linear linear response.response.
PHYPHY--2464 2464 Pres. 5 Human EarPres. 5 Human Ear
Neuronal Decoding of Sound (Schematic)Neuronal Decoding of Sound (Schematic)
Frequency response Frequency response localized in Cochlealocalized in Cochlea
High Frequency
Low Frequency
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Neuronal Response to SoundNeuronal Response to Sound•• Frequency Frequency →→ WhereWhere? The location in the ? The location in the
Cochlea at which the Cochlea at which the stereociliastereocilia are stimulated.are stimulated.•• Intensity Intensity →→ How manyHow many? The number of ? The number of HC that HC that
are stimulated by the sound determines the are stimulated by the sound determines the perceived intensity (loudness).perceived intensity (loudness).
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VorsichtVorsicht! Caution! ! Caution! Repeated acoustic trauma can cause permanent and Repeated acoustic trauma can cause permanent and
profound hearing loss or deafness.profound hearing loss or deafness.
If you have experienced temporary hearing loss due If you have experienced temporary hearing loss due to loud sounds you have had a warning.to loud sounds you have had a warning.
StereociliaStereocilia do regenerate daily (but cannot do regenerate daily (but cannot overcome loud sound abuse).overcome loud sound abuse).
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Example Damage from Extreme Acoustic TraumaExample Damage from Extreme Acoustic Trauma
Control, not exposedControl, not exposed After ExposureAfter Exposure
Guinea Pig Guinea Pig StereociliaStereocilia damage (120 dB sound)damage (120 dB sound)
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How does Anatomy affect perception?How does Anatomy affect perception?•• Frequency responseFrequency response•• Loudness perceptionLoudness perception•• Phase insensitivityPhase insensitivity•• DeafnessDeafness
•• Disruption of “acoustic chain.”Disruption of “acoustic chain.”•• Nerve death.Nerve death.
•• RemediesRemedies•• Restore chain or increase amplitudeRestore chain or increase amplitude
Summary (concluded):Summary (concluded):•• Physiology determines function.Physiology determines function.•• No phase detection mechanism.No phase detection mechanism.•• Large “nonLarge “non--linear” range of 12 orders of linear” range of 12 orders of magnitude in intensitymagnitude in intensity•• Three (3) orders of magnitude in frequency (20 Hz Three (3) orders of magnitude in frequency (20 Hz to 20 kHz).to 20 kHz).•• Trauma (due to loud sounds) is a cause of Trauma (due to loud sounds) is a cause of deafness.deafness.