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TRG-TRC007-EN 27
period two
Sound Perception and
Rating Methods
notes
The phon is another descriptor used to indicate loudness with a single number.
The loudness of a sound, expressed in phons, is equal to the sound- pressure
level of a standard sound, at 1,000 Hz, that is considered equally loud. For
example, a sound pressure level of 40 dB at 1,000 Hz is considered to have a
loudness of 40 phons. Any sound that falls on this same loudness curve, at any
frequency, would also be described as having a loudness equal to 40 phons.
While the phon scale is logarithmic, the sone is the linear equivalent to the
phon. In principle, the sone scale is linear when compared to the response of
the human ear. For example, two sones is twice as loud as one sone, and half
as loud as four sones.
While the phon and sone scales are not widely used, some HVAC equipment,
primarily non-ducted fans and power ventilators, is still rated in sones. AMCA
Standard 301, Methods for Calculating Fan Sound Ratings from Laboratory Test
Data, provides a method for calculating the sone rating from octave-band data.
Use caution when comparing equipment based on sones. Multiple methods
exist for calculating a sone rating, and they provide different results.
frequency, Hz
frequency, Hz
50
50
100
100
200
200
500
500
1,000
1,000
2,000
2,000
5,000
5,000
20
20
10,000
10,000
120
120
100
100
80
80
60
60
40
40
20
20
0
0
sound pressure, dB ref 20
sound pressure, dB ref 20
m
m
Pa
Pa
Phon and Sone
10
10
20
20
30
30
40
40
50
50
60
60
70
70
80
80
90
90
100
100
110
110
120
120
loudness level (
loudness level (
phons
phons
)
)
Figure 31