Appendix
Typical 'A' Weighted dB levels
Frequency Weighting Graph
Frequency Weighting
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
100
1000
10000
Frequency (Hz)
dB
(re
lat
ive
)
'A' Weighting
'C' Weighting
140
120
100
80
60
40
20
0
130
110
90
70
50
30
10
50 HP Siren (100')
Jet take-off (200')
Riveting machine
Subway (20')
Pneumatic drill (50')
Vacuum cleaner (10')
Large store
Small office
Residential area
(night)
Whisper (5')
Threshold of hearing
Chain saw
Boiler room
Freight train (100')
Speech (1')
Large Office
Residence
Sound studio
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Air Concern Ltd, Building 173 Curie Avenue Harvell Didcot, Oxfordshire