Physics 1251 The Science and Technology of Musical Sound Unit 2 Session 14 MWF Human Perception:...

Physics 1251Physics 1251The Science and The Science and

Technology of Musical Technology of Musical SoundSound

Physics 1251Physics 1251The Science and The Science and

Technology of Musical Technology of Musical SoundSound

Unit 2Unit 2

Session 14 MWFSession 14 MWF

Human Perception: Human Perception: LoudnessLoudness

Unit 2Unit 2

Session 14 MWFSession 14 MWF

Human Perception: Human Perception: LoudnessLoudness

Physics 1251Physics 1251 Unit 2 Session 14Unit 2 Session 14Human Perception: LoudnessHuman Perception: Loudness

Foolscap Quiz:Foolscap Quiz:A sound has an intensity of 0.005 W/mA sound has an intensity of 0.005 W/m22. . What is the Sound Intensity Level (SIL) in What is the Sound Intensity Level (SIL) in dB?dB?

Pass the sheet to your left when you finish. Pass the sheet to your left when you finish. Please do not use your notes. Thank Please do not use your notes. Thank you!you! SIL = 10 Log ( I / ISIL = 10 Log ( I / Ithreshold threshold ))

SIL = 10 Log ( .005/ (1 x10 SIL = 10 Log ( .005/ (1 x10 -12-12))))

SIL = 10 Log ( 5 x 10SIL = 10 Log ( 5 x 1099 ) = 97 dB. ) = 97 dB.


11′ Lecture:′ Lecture:• LoudnessLoudness is the magnitude of the sensation is the magnitude of the sensation

produced by a sound; the “amount” of produced by a sound; the “amount” of sound.sound.

• Loudness (in Loudness (in sonesone) is how many times larger ) is how many times larger (or smaller) the sensation is judged to be, (or smaller) the sensation is judged to be, relative to a tone of SIL=40 dB at 1000 Hz.relative to a tone of SIL=40 dB at 1000 Hz.

• Loudness LevelLoudness Level (in phon) is equal to the SIL (in phon) is equal to the SIL at 1000 Hz that produces the same at 1000 Hz that produces the same magnitude of sensation.magnitude of sensation.


The Human Ear is a “non-linear The Human Ear is a “non-linear Sensor”Sensor”PhysicsPhysics ⇒ ⇒ Physiology Physiology

⇒⇒PerceptioPerceptionn


Human Aural Response:Human Aural Response:

• Intensity Intensity →→ LoudnessLoudness

• Frequency →Frequency → PitchPitch

• Vibration Recipe Vibration Recipe →→ TimbreTimbre

Frequency Frequency

Vibration Vibration

RecipeRecipe IntensityIntensity

Vibration recipeVibration recipe

IntensityIntensity

FrequencyFrequency

But…But…


““Resonant” Frequency vsResonant” Frequency vs

Location on Basilar Location on Basilar MembraneMembrane

20 kHz20 kHz

20 20 HzHz

Range of Range of Maximum Maximum SensitivitySensitivity


The Density The Density of Hair Cof Hair Cells (HC)ells (HC)

varies with distancevaries with distance

from the stapes.from the stapes.

Fewer Fewer HCHC

Fewer HCFewer HC

More HCMore HC


Fletcher- Munson DiagramFletcher- Munson Diagram

Fletcher and Munson (1933) Fletcher and Munson (1933) J. Acoust. Soc. Am. J. Acoust. Soc. Am. 55, 82-108, 82-108Frequency (Hz)Frequency (Hz)

SIL SIL (dB)(dB)

101020203030404050506060707080809090

100100110110120120130130

Loudness Loudness (phon)(phon)


80/2080/20The The Fletcher-Munson DiagramFletcher-Munson Diagram is a plot of is a plot of the SIL (in dB) versus frequency for the the SIL (in dB) versus frequency for the SIL required to produce an equal SIL required to produce an equal sensation as that produced at 1000 Hz. sensation as that produced at 1000 Hz.

80/2080/20The contours are of equal The contours are of equal loudness levelloudness level..

80/2080/20The unit of loudness level is the The unit of loudness level is the phonphon..




SIL SIL (dB)(dB)

101020203030404050506060707080809090

100100110110120120130130


Auditory Demonstration #6Auditory Demonstration #6Houstma and RossingHoustma and Rossing

Institute for Perception ResearchInstitute for Perception Research (IPO)(IPO)Einhoven, The NetherlandsEinhoven, The Netherlands

&&Acoustical Society of AmericaAcoustical Society of AmericaTrack 17,18Track 17,18

Count the number of tones you thatCount the number of tones you that

can hear at each of the following can hear at each of the following frequencies:frequencies:

125, 250, 500, 1000, 2000, 4000, 8000 Hz.125, 250, 500, 1000, 2000, 4000, 8000 Hz.


Using the Fletcher- Munson DiagramUsing the Fletcher- Munson Diagram

Determine the SIL necessary to Determine the SIL necessary to have a Loudness Level of 70 have a Loudness Level of 70 phon at 200 Hz, 2000 Hz and phon at 200 Hz, 2000 Hz and 10,000 Hz.10,000 Hz.

Frequency (Hz)Frequency (Hz)

SIL SIL (dB)(dB)

4040

9090

1010

3030

6060

8800

110110

130130

2020

5050

7070

100100

120120


Using the Fletcher- Munson DiagramUsing the Fletcher- Munson DiagramDetermine the SIL necessary to have a Loudness Determine the SIL necessary to have a Loudness

Level of 70 phon at 200 Hz, 2000 Hz and 10,000 Level of 70 phon at 200 Hz, 2000 Hz and 10,000 Hz.Hz.




SIL SIL (dB)(dB)

101020203030404050506060707080809090

100100110110120120130130

Equal Equal LoudnessLoudness (70 phon) (70 phon)

200 Hz—70 200 Hz—70 dBdB2 kHz—70 2 kHz—70 dBdB10 kHz—75 10 kHz—75

dBdB

Frequency (Hz)Frequency (Hz)

SIL SIL (dB)(dB)

4040

9090

1010

3030

6060

8080

110110

130130

2020

5050

7070

100100

120120


Using the Fletcher- Munson DiagramUsing the Fletcher- Munson DiagramUsing the F-M Diagram determine the Loudness Using the F-M Diagram determine the Loudness

Level of an 80 dB tone at 100 Hz, 400 Hz and Level of an 80 dB tone at 100 Hz, 400 Hz and 8000 Hz.8000 Hz.




SIL SIL (dB)(dB)

101020203030404050506060707080809090

100100110110120120130130

73 73 phonphon81 phon81 phon72 phon72 phon

Loudness Loudness (phon)(phon)

80 dB




SIL SIL (dB)(dB)

101020203030404050506060707080809090

100100110110120120130130


Since the Loudness Level for a given frequency can be Since the Loudness Level for a given frequency can be approximated by a linear function of the Intensity approximated by a linear function of the Intensity Level,Level,

Thus:Thus:

LL LL ≈ ≈ AAff (SIL – SIL (SIL – SILthreshold threshold ),),

80/2080/20One of the settings of a Sound Level Meter One of the settings of a Sound Level Meter (filter switch “A”) modifies the calibration of (filter switch “A”) modifies the calibration of the instrument to account for the frequency the instrument to account for the frequency dependence of human hearing.dependence of human hearing.

80/2080/20The Sound Level is reported then as “dBA.”The Sound Level is reported then as “dBA.”


Sound Level MeterSound Level Meter

• Measures Measures

Sound Intensity Level Sound Intensity Level

(SIL) in dB(SIL) in dB


LoudnessLoudness

80/2080/20 A subjective measure of the magnitude A subjective measure of the magnitude of auditory sensation is called of auditory sensation is called LoudnessLoudness and is measured in and is measured in sonesone. In this system, . In this system, one listens to two sounds and judges one listens to two sounds and judges how much louder or softer a test sound how much louder or softer a test sound is compared to the referenceis compared to the reference..

For example, a sound of 2 sone sounds twice as For example, a sound of 2 sone sounds twice as loud as a tone of 1 sone.loud as a tone of 1 sone.


Auditory Demonstration #7Auditory Demonstration #7Houstma and RossingHoustma and RossingInstitute for Perception ResearchInstitute for Perception Research (IPO)(IPO)Einhoven, The NetherlandsEinhoven, The Netherlands

&&Acoustical Society of AmericaAcoustical Society of AmericaTrack 19,20Track 19,20

Estimate how loud each of the sound samplesEstimate how loud each of the sound samples is, compared to the reference sound is, compared to the reference sound

sample. sample.

The reference is presented first along with the The reference is presented first along with the loudest and softest sounds. loudest and softest sounds.


Loudness ScalingLoudness Scaling

Loudness L Loudness L ∝∛ I ∝∛ I

80/2080/20Thus, an eight (8) singer ensemble Thus, an eight (8) singer ensemble

sounds about twice (2x) as loud as a sounds about twice (2x) as loud as a

soloist. Because soloist. Because ∛∛8 = 2. 8 = 2.

Likewise, a choir of sixty-four (64) sounds Likewise, a choir of sixty-four (64) sounds

about four (4x) times louder than a soloist. about four (4x) times louder than a soloist.

∛∛64 = 4.64 = 4.


Summary:Summary:• LoudnessLoudness is the magnitude of the is the magnitude of the

sensation produced by a sound; it is sensation produced by a sound; it is measured in sone.measured in sone.

• Loudness LevelLoudness Level (in phon) is equal to the (in phon) is equal to the SIL at 1000 Hz that produces the same SIL at 1000 Hz that produces the same magnitude of sensation.magnitude of sensation.

• Loudness increases approximately with Loudness increases approximately with the the cube rootcube root of intensity. of intensity.


Summary:Summary:• The loudness depends on The loudness depends on

frequency.frequency.


Examination 1Examination 1Physics 1251.001 2003C

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Physics 1251 The Science and Technology of Musical Sound Unit 2 Session 14 MWF Human Perception:...

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