Bathroom Fan Ductwork Noise

8 Jan 2007
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United Kingdom
Hi all.

Rather then resurrect a 2yr old thread I created, I thought it better to ask another question re: ductwork noise. My bathroom ventilation consists of two separate inlets (one above shower, one above bath) connected via a swept "T", all in 125mm Rigid Ductwork and powered by a Manrose MFT125 inline fan. The total ductwork length is about 6M. The extraction is perfect, no problems there. However, the noise level is pretty bad. I've made all connections with neoprene tape (so the duct sections aren't actually physically touching each other [and they are well supported]) which did help a bit but it's still pretty loud.

I've replaced the external backdraught shutter with a cheap motorised shutter, tied into the fan run-on, so I've managed to get rid of the "clattering" noise but the actual roaring when the fan is in use is still pretty loud so I was considering buying one of THESE duct silencers to see if it would cut down on the noise any. I was proposing to put it in between the motor and the bathroom inlets as I'm not fussed about the noise outside. I'm not under any delusions that I will be able to cancel it all out as I'm aware rigid ducting will always a be a bit noisier but I'd like to reduce it to as much as possible.

Has anyone got any experience of these types of fittings and whether they actually do cut a good proportion of the noise out, or are they of the "snake oil" variety :LOL:

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Cover with insulation, or try a new fan?

The ductwork is already well insulated with a rockwool and silver bubble-wrap coating. In the loft, where the fan and ductwork are, you can hardly hear it running. I'm guessing the majority of the noise is from the airflow hence the reason I was wondering if the silencer I linked to would actually be of any use.

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