Silencers

A duct silencer – or muffler – is an acoustically lined section of ducting that fits inline after your fan. Sound travels down a duct as readily as air does, and a silencer absorbs it before it reaches the outlet.

Where the noise actually comes from

Three separate sources, and they need different fixes:

• Motor noise – the fan itself. Fixed by a silenced box fan or an EC fan turned down.
• Air noise – turbulence in the ducting. Fixed by a silencer, and by pulling flexible ducting taut rather than leaving it concertinaed.
• Vibration – the fan transmitting through whatever it is mounted on. Fixed by hanging it on rope ratchets or straps rather than bolting it to a wall or a tent frame.

A silencer only addresses the second. If your problem is vibration through a joist, a silencer will not help – hang the fan instead.

Fitting it

• After the fan, on the exhaust side. That is where the noise is loudest.
• Match the diameter to your fan and ducting. A step down chokes airflow.
• Longer is quieter. More lined length means more absorption.
• Expect a small airflow cost – typically a few percent. Worth it if noise is what stands between you and running the room.

The cheap wins first

Before buying anything: hang the fan on rope ratchets so it touches nothing solid, pull the ducting taut and cut it to length, and turn the fan down if you have the headroom. Between them those three fix most noise complaints for nothing.

Related

See extraction fans, ducting and fittings and speed controllers.

Why buy from The Hydro Bros?

We are a hydroponics shop in Croydon and plenty of our customers grow in flats. Tell us where the noise is and we will tell you what actually fixes it. Discreet UK and European delivery, and excellent customer reviews on Trustpilot.