Sound Attenuation - Duct split to Terminals

Estimating sound attenuation where ducts splits to terminals. Splitting ducts to terminals will reduce the sound power level transferred to each terminal based on the reduced volume of air.

Number of Equal TerminalsSound Attenuation (dB)
10
23
34.77
46
56.99
67.78
89.03
1010

How Sound Attenuation Works

When a duct splits into multiple equal terminals, the sound power level (LN) is reduced according to the reduced volume of air flowing through each terminal.

Formula

The sound attenuation for equal terminals can be calculated as:

Attenuation (dB) = 10 × log₁₀(Number of Terminals)

Example

For a duct that splits into 4 equal terminals, the sound attenuation from duct to each terminal is approximately 6 dB.