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Sound attenuation vs. change in duct size.
Sound attenuation when changing duct areas or dimensions:
dL = 10 log( ( 1 + A 1 / A 2 ) 2 / 4 (A 1 / A 2) ) (1)
dL = noise attenuation (dB)
A 1 = inlet area (m 2)
A 2 = outlet area (m 2)
Note! - valid only for sharp changes.
Example - Attenuation when changing the size of a duct
The attenuation of noise when the ratio between area before and after
Acan be calculated as 1 / A 2 = 5 -
dL = 10 log( ( 1 + 5 ) 2 / 4 (5))
= 2.5 dB
Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.
Chamber sound attenuation.
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Change in Duct Area and Noise Attenuation. [online] Available at: https://www.engineeringtoolbox.com/duct-area-change-noise-attenuation-d_1408.html [Accessed Day Month Year].
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