Decibels, Phons, And Sones Worksheet With Answer Key
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4Decibels, Phons, and Sones
Table 1: deciBel Ratings of Several Sounds
The rate at which sound energy reaches a
Sound Source
Intensity
deciBel
given cross-sectional area is known as the
-12
2
Weakest Sound Heard
sound
intensity. There is an abnormally
1 x 10
W/m
0.0
large range of intensities over which
-11
2
Rustling Leaves
1 x 10
W/m
10.0
humans can hear. Given the large range, it
-9
2
Quiet Library
1 x 10
W/m
30.0
is common to express the sound intensity
-7
2
Average Home
1 x 10
W/m
50.0
using a logarithmic scale known as the
-6
2
Normal Conversation
1 x 10
W/m
60.0
decibel
scale. By measuring the intensity
-4
2
Phone Dial Tone
1 x 10
W/m
80.0
level of a given sound with a meter, the
-3
2
Truck Traffic
1 x 10
W/m
90.0
deciBel rating can be determined.
-1
2
Chainsaw, 1 m away
1 x 10
W/m
110.0
Intensity values and decibel ratings for
several sound sources listed in Table 1.
The decibel scale and the intensity values it is based on is an objective measure of a sound.
While intensities and deciBels (dB) are measurable, the loudness of a sound is subjective. Sound
loudness varies from person to person. Furthermore, sounds with equal intensities but different
frequencies are perceived by the same person to have unequal loudness. For instance, a 60 dB
sound with a frequency of 1000 Hz sounds louder than a 60 dB sound with a frequency of 500
Hz. The unit
phon
is used to indicate an individual’s perception of loudness. By definition, 1
phon is equivalent to 1 deciBel at 1000 Hz (1 kHz).
Figure 1 shows several equal loudness
Figure 1: Equal Loudness Curves
curves. The curves were determined
experimentally. Volunteers were subjected
to a 1 kHz sound at 60 dB; this is a loudness
of 60 phon. Sounds with different
frequencies were then played; the volunteer
adjusted the decibel level until it was
perceived to have the same loudness as it
had at 1000 Hz. This was repeated for
varying frequencies to generate the entire
60-phon curve. To create an 80-phon curve,
subjects were exposed to 1 kHz sounds at 80
dB. For other frequencies, they adjusted the
decibel level until it was perceived to be of
equal loudness as the 1 kHz sound. Figure 1
represents an average of the results for
many individuals.
The
sone scale
is a third scale associated
Figure 2: The Sone Scale
with the loudness of a sound. The sone
0.25 0.5
4
1
2
8 16 32 64
Sones
scale is based on the observation that a 10
phon increase in a sound level is most
10
20
30
40
50
60
70
80
90
Phons
100
often perceived as a doubling of loudness.
According to the sone scale, a 1 sone sound is defined as a sound whose loudness is equal to 40
phons. Figure 2 is generated based on these assumptions.
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