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6. NOISE CRITERION CURVES
90
80
70
60
50
40
30
20
10
63 125 250 500 1000 2000 4000 8000
APPROXIMATE
THRESHOLD OF
HEARING FOR
CONTINUOUS
NOISE
NC-60
NC-50
NC-40
NC-30
NC-20
NC-70
OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR
BAND CENTER FREQUENCIES, Hz
Hi
NOTCH
Lo
49
SPL(dB)
44
LINE
90
80
70
60
50
40
30
20
10
63 125 250 500 1000 2000 4000 8000
APPROXIMATE
THRESHOLD OF
HEARING FOR
CONTINUOUS
NOISE
NC-60
NC-50
NC-40
NC-30
NC-20
NC-70
OCTAVE BAND SOUND PRESSURE LEVEL, dB re 0.0002 MICRO BAR
BAND CENTER FREQUENCIES, Hz
Hi
NOTCH
Lo
48
SPL(dB)
41
LINE
Wall
Unit
3.3ft
3.3ft
Ambient temperature 80˚F
Test conditions are based on JIS Z8731
PKH18FL
PKH24FL
PKH30FL
PKH36FL
OC276-A-1.qxp 03.11.25 9:04 AM Page 15