Sound data, roof and wall fans

Equations and calculations for sound data

The fans must be installed with silencers in the duct system in accordance with the sound requirements of the ventilated premises.

To meet current standards the duct system should be insulated for sound, thermal loss and condensation.

Sound output levels are used as the basis for calculating the sound pressure level in the fan's operating range, and the level of silencing required in the duct system itself.

Explanation of terms


Correction factor for calculating sound output in the octave band

KWA  Correction factor for calculating A-weighted sound output
KpA  Correction value for calculating A-weighted  sound pressure
LW Sound output level in dB, reference 1pW, Tolerance: ±3 dB
I  higher operating range    
II lower operating range
LW1 Sound output level in extract duct LW1 = LWA1 + KW (LWA1 to be read off on curve)
LW3: Sound output level in surroundings LW3 = LWA1 + KW (LWA1 to be read off on curve)
LWA3: A-weighted sound output level in surroundings LWA3 = LWA1 + KWA (LWA1 to be read off on curve)

Sound pressure level dB (A) at 10 m distance for hemispherical sound propagation in free field and with insulated connection ducts

LWA1 to be read off - LpA3 = LWA1 + KpA (10 m) , sound pressure level at 20 m distance: LpA3 (20 m) = LpA3 (10 m) - 6 dB


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