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Attenuation - Duct Bend    1/1

Strutt|Mechanical Services|Duct Elements|Bend inserts attenuation due to bends in ductwork into the active row of the worksheet.

Insertion loss data can be sourced from the 2019 ASHRAE Handbook - HVAC Applications (Tables 22, 23 and 24) or the Arup Sound and Vibration in Mechanical Services Design (Blue Book - Tables 14, 15 and 16).

The input required is the characteristic dimension of the duct, width (w) in the same plane as the change in direction of the duct, number of bends and the type of bend (plus the lining thickness, for some calculations).

Arup Mechanical Services Guide is based on the Sound Research Laboratories book "Noise Control in Building Services" and references octave band attenuation according to the range that the duct width is within.

ASHRAE calculates the attenuation for bends as follows:

CIBSE calculates the attenuation for bends as follows:


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