Design
D - 24
(3) Sound level attenuation through a noise barrier
Sound attenuation of an outdoor unit at a reception point behind a noise barrier or building depends upon the
frequency and difference in path length.
δ:difference in path distance
δ=(A+B)-d
Example 1
Reception poin
٨
d
B
A
building
Outdoor unit
As close as possible (however, ensure intake and exhaust space
and service and maintenance space)
1m or less
Effective area
B
A
Sound
barrier
Outdoor unit
When bent, longer than
this line
Several
times the
barrier
height
Sound
barrier
Outdoor
Sound reception
point
٨
Sound path difference (m)
Refraction attenuation (phon)
Sound
source
Reception
point
● The barrier should be positioned as close as possible to the
outdoor unit (sound source).(Figure 3)
(take care to ensure air intake and exhaust space, and service
and maintenance space)
● The barrier should be sufficiently higher than the top of the
outdoor unit (Figure 3).
(however, not more than 1m higher)
● The width of the barrier on both sides should be more than
several times the height. Where this is not possible then as
shown in Figure 4, the barrier should bend around the unit.
Fig. 3 Noise barrier
Fig. 4 Noise barrier
Fig. 2 Diffraction attenuation
6. Sound-proofing measures
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