Box ventilator - assumptions 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. 



Correction factor for calculating sound output in the octave band


Correction factor for calculating A-weighted sound output 


Correction value for calculating A-weighted sound pressure

 LW  Sound output level in dB, reference 1pW, Tolerance: ±3 dB
I - IV Operating ranges
LW1  Sound output level in extract duct (measured according to ISO 5136) LW1 = LWA1 + KW  (LWA1 to be read off on curve)
LW2:  Sound output level in pressure duct (measured according to ISO 5136) LW1 = LWA1 + KW (LWA1 to be read off on curve)
LW3:  Sound output level in surroundings (measured according to ISO 3744) 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

 LpA3 = LWA1 + KpA (LWA1 to be read off on curve)


See calculation example for BESF200-4-1FC

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