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GENERAL ACOUSTIC INFORMATION
H
© FANTECH
2016
NOISE CONTROL PRODUCTS
ATTENUATOR PASSAGE VELOCITY
For industrial applications and to determine attenuator re-generated noise, the passage
velocity must be found as described below:
ATTENUATOR RE-GENERATED/
AIR FLOW GENERATED NOISE :
As air passes through an attenuator it will frequently pass at speeds as much as 2 to
4 times the air flow speed in the duct. Moving air creates noise, so in noise sensitive
rooms and installations where attenuators are placed close to air grilles and terminals,
particular care must be taken to ensure that this does not become the dominating
noise source. The relationship between airway velocity and generated noise is shown
below for rectangular attenuators.
SPECTRUM CORRECTIONS
FOR AIRWAY VELOCITY :
6 8 10
20
40
40
50
60
70
80
90
Airway Velocity, m/s
BaseSoundPower Level, L
W
500
1000
2000
4000
Splitter height
Airway
Velocity
m/sec
63 125 250 500 1k 2k 4k 8k
<8
-2
-6
-7
-10 -12 -16 -19 -22
>8 & <32
-3
-5
-8
-7
-8
-10 -13 -15
>32
-3
-6
-10 -7
-7
-8
-10 -12
Octave Band Centre Frequency, Hz
H-26