Extractor Fan Noise

[DIYWell]

Any idea how to reduce noise?

It's a MF100T on 100mm rigid ducting about 3m long in total. The inline fan is in the middle. It's set to the 'slow' speed so 'only' pulls 180m3/hr

I've checked the exhaust isn't blocked and the air is passing freely. I've mechanically isolated the duct from the fan, and that's not reduced the noise. so I doubt replacing with flexiducting would make a difference I've disconnected the entrance vent to see if that's the cause of the noise but that made no significant difference.

Any suggestions?

 

[Burnerman]

Could it be the fan motor reverberating through the ceiling joists, do you think?
Pack the fan with some lengths of carpet or whatever to see if that improves things.
John

 

[DIYWell]

It's more of a down-the-tube sound than a through-the-ceiling one. Also it it were the latter I'd expect to hear it in different places rather than quite localised

 

[foxhole]

Vibration of the fan mount will travel down the tube as well as thru the ceiling, I hung my in-line fan from springs to reduce noise transmission.

 

[Grenage]

I did the same as Foxhole, suspending an ACM100T by bungee cords. There's still plenty of 'air noise', but mainly due to flexible ducting - which I couldn't avoid.