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GENERAL ACOUSTIC INFORMATION
H
H-25
NOISE CONTROL PRODUCTS
© FANTECH
2016
Octave band centre frequency, Hz
Octave band sound pressure level, dB
63 125
2k
250
4k
500
8k
1k
10
20
60
30
70
50
80
90
40
Noise Rating Curves
70
65
60
55
50
45
40
35
30
25
20
15
Notes
The dB(A) equivalent of the NR values would be approximately 5
dB(A) higher in each instance.
NR and PNC curves are designed to be used with broadband,
constant noise sources (eg. motors, engines), and do not allow
for the increased annoyance associated with tonal, or pulsating
noises.
The Noise Rating (or NR contour) curves were proposed by
Kosten and Van Os (1962) to rate internal noise levels.
To use the curves, plot the noise spectrum onto the NR curves
grid. The Noise Rating is defined as that curve which touches
the highest point on the sound pressure spectrum.
Some acoustic consultants prefer to use the Preferred Noise
Criterion (PNC) curves. These curves were designed by Beranek
(1971) to achieve a more acceptable noise quality and lower the
allowable levels of low and high frequency noises.
To use the curves, plot the noise spectrum onto the PNC curves
grid. The Preferred Noise Criterion is defined as that curve
which touches the highest point on the sound pressure
spectrum.
Octave band centre frequency, Hz
Octave band sound pressure level, dB
63 125
2k
250
4k
500
8k
1k
10
20
60
30
70
50
80
0
40
Preferred Noise Criteron Curves
65
60
55
50
45
40
35
30
25
20
15
NR & PNC Ratings