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Noise Attenuation in Chambers

Chamber sound attenuation.

Chamber noise attenuation

Noise attenuation in a chamber:

dL = 10 log( 1 / Ao (cos(θ) / 2 π s2  + (1 - α) / (α A)))                              (1)

where

dL = sound attenuation (dB)

Ao = outlet area (m2)

A = chamber inside surface area (m2)

θ = angle between inlet and outlet (degrees)

s = distance between inlet and outlet (m)

α = inside surface sound absorption coefficient 

Example - Attenuation in a Chamber

The attenuation in a chamber lined with mineral wool with a sound absorption coefficient α = 0.65, inside surface area A = 16 m2, outlet area Ao = 0.25 m2, distance between inlet and outlet s = 2 m, angle between inlet and outlet α = 45o, can be calculated as

dL = 10 log( 1 / (0.3 m2) (cos(45o) / 2 π (2 m)2  + (1 - 0.65) / (0.65 (16 m2))))

    = 17.3 dB

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