Quieting a loud bath exhaust fan.

woobagooba

New bathrrom with remote fan. Two ceiling vents Y into the remote fan input about 15 feet away, then out the side of the building it goes. Similar install at another location is whisper quiet. This install … very loud. The difference? The quiet one is flex ducted, the loud one is hard piped. Ceilings are closed. Do I have any options to quiet the roar?

Dave Carpentier

Presumably there is access to the inline fan ? Could maybe play around there to figure out which of the 3 pipes is making a harmonic or if it's the fan itself (vibrating) ?

EBEBRATT-Ed

Maybe putting in a damper and closing it slightly would help

woobagooba

Here is my access. You can barely see the two 4" pipes coming into the fan, then the 6" pipe to the outside.

Dave Carpentier

Looks like a treat to service lol. Looks like you cant get to the input side at all.
Is it an air rushing/swooshing sound ? Whistle ? Howl ? Low pitched hum ?
Can the fan speed be changed ?

woobagooba

Loud low frequency whooshing sound. I will check the fan speed detail.