Physics 1251
The Science and Technology
of Musical Sound
Unit 2
Session 14 MWF
Human Perception: Loudness
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Foolscap Quiz:
A sound has an intensity of 0.005 W/m2.
What is the Sound Intensity Level (SIL) in dB?
Pass the sheet to your left when you finish.
Please do not use your notes. Thank you!
SIL = 10 Log ( I / Ithreshold )
SIL = 10 Log ( .005/ (1 x10 -12))
SIL = 10 Log ( 5 x 109 ) = 97 dB.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
1′ Lecture:
•
Loudness is the magnitude of the sensation
produced by a sound; the “amount” of sound.
•
Loudness (in sone) is how many times larger
(or smaller) the sensation is judged to be,
relative to a tone of SIL=40 dB at 1000 Hz.
•
Loudness Level (in phon) is equal to the SIL
at 1000 Hz that produces the same magnitude
of sensation.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
The Human Ear is a “non-linear Sensor”
Physics ⇒
Physiology
⇒ Perception
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Human Aural Response:
•
•
•
Frequency
Intensity →
But…
Vibration Recipe
Intensity
Frequency →
Vibration recipe
Intensity
Vibration Recipe →
Frequency
Loudness
Pitch
Timbre
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
“Resonant” Frequency vs
Location on Basilar Membrane
20 kHz
Range of Maximum
Sensitivity
20 Hz
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
The Density
of Hair Cells (HC)
varies with distance
from the stapes.
Fewer HC
More HC
Fewer HC
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Fletcher- Munson Diagram
SIL
(dB)
Loudness (phon)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
Fletcher and Munson (1933) J. Acoust. Soc. Am. 5, 82-108
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
80/20The
Fletcher-Munson Diagram is a plot of
the SIL (in dB) versus frequency for the SIL
required to produce an equal sensation as
that produced at 1000 Hz.
80/20The
contours are of equal loudness level.
80/20The
unit of loudness level is the phon.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Fletcher- Munson Diagram
SIL
(dB)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
Fletcher and Munson (1933) J. Acoust. Soc. Am. 5, 82-108
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Auditory Demonstration #6
Houstma and Rossing
Institute for Perception Research (IPO)
Einhoven, The Netherlands
&
Acoustical Society of America
Track 17,18
Count the number of tones you that
can hear at each of the following frequencies:
125, 250, 500, 1000, 2000, 4000, 8000 Hz.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Using the Fletcher- Munson Diagram
Determine the SIL necessary to have a
Loudness Level of 70 phon at 200 Hz,
2000 Hz and 10,000 Hz.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Using the Fletcher- Munson Diagram
Determine the SIL necessary to have a Loudness Level of 70 phon
at 200 Hz, 2000 Hz and 10,000 Hz.
SIL
(dB)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Fletcher- Munson Diagram
SIL
(dB)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
200 Hz—70 dB
2 kHz—70 dB
10 kHz—75 dB
Equal Loudness
(70 phon)
Fletcher and Munson (1933) J. Acoust. Soc. Am. 5, 82-108
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Using the Fletcher- Munson Diagram
Using the F-M Diagram determine the Loudness Level of an 80 dB
tone at 100 Hz, 400 Hz and 8000 Hz.
SIL
(dB)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Fletcher- Munson Diagram
SIL
(dB)
80 dB
130
120
110
100
90
80
70
60
50
40
30
20
10
73 phon
81 phon
72 phon
Loudness (phon)
Frequency (Hz)
Fletcher and Munson (1933) J. Acoust. Soc. Am. 5, 82-108
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Fletcher- Munson Diagram
SIL
(dB)
130
120
110
100
90
80
70
60
50
40
30
20
10
Frequency (Hz)
Fletcher and Munson (1933) J. Acoust. Soc. Am. 5, 82-108
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Since the Loudness Level for a given frequency can be
approximated by a linear function of the Intensity
Level,
Thus:
LL ≈ Af (SIL – SILthreshold ),
80/20One
of the settings of a Sound Level Meter
(filter switch “A”) modifies the calibration of the
instrument to account for the frequency
dependence of human hearing.
80/20The
Sound Level is reported then as “dBA.”
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Sound Level Meter
•
Measures
Sound Intensity Level
(SIL) in dB
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Loudness
A subjective measure of the magnitude of
auditory sensation is called Loudness and is
measured in sone. In this system, one listens
to two sounds and judges how much louder or
softer a test sound is compared to the
reference.
80/20
For example, a sound of 2 sone sounds twice as loud as
a tone of 1 sone.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Auditory Demonstration #7
Houstma and Rossing
Institute for Perception Research (IPO)
Einhoven, The Netherlands
&
Acoustical Society of America
Track 19,20
Estimate how loud each of the sound samples
is, compared to the reference sound sample.
The reference is presented first along with the
loudest and softest sounds.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Loudness Scaling
Loudness L ∝∛ I
80/20Thus,
an eight (8) singer ensemble sounds
about twice (2x) as loud as a soloist. Because
∛8 = 2.
Likewise, a choir of sixty-four (64) sounds about
four (4x) times louder than a soloist. ∛64 = 4.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Summary:
•
•
•
Loudness is the magnitude of the sensation
produced by a sound; it is measured in sone.
Loudness Level (in phon) is equal to the SIL
at 1000 Hz that produces the same magnitude
of sensation.
Loudness increases approximately with the
cube root of intensity.
Physics 1251
Unit 2 Session 14
Human Perception: Loudness
Summary:
•
The loudness depends on frequency.
Physics 1251

Unit 2 Session 14
Human Perception: Loudness
Examination 1
Physics 1251.001 2003C
Examination #1
35
30
25
20
15
10
5
0
F
D
C
B
A