Greeting.
Hope to get your kind advise for the noise level in machinery spaces like generator room.
For Example, I have one supply and one exhaust fan which have 85 dB(A). And the duct length is around 40 m. And the velocity in duct is 8m/sec. at the air terminal is 5 m/sec. Is there any formula to calculate the noise level caused by the ventilation system?Or we just need to consider room noise level is same as the fan noise level.

Regards