Climate & Ventilation — Silencers

Almost everyone buying a silencer is buying it for the wrong noise. Extraction makes two, they travel by different routes, and a silencer works on one of them. That distinction decides whether you are finished on this page.

Airborne noise and structure-borne noise

Airborne noise travels with the air: the rush through the duct and the hum the fan sends down the run. That is what a silencer catches, in the foam or mineral wool in its wall. Structure-borne noise travels through the building. A fan strapped tight to a tent pole passes its vibration into the frame, and the fabric works as a loudspeaker. You hear that in the room while your duct is dead quiet, and no silencer fixes it. For that you decouple the fan, with hanging straps or a rubber sleeve from Ducting.

A separate silencer behind the fan you already own

The AC Infinity Pipe Silencer is chosen on connection diameter, in Ø100, Ø150 and Ø200 mm, with a neoprene lining inside galvanised steel. The Can-Fan silencers are chosen on diameter and length both: Ø125 and Ø160 at 45 cm, Ø250 at 50 cm. Longer damps more, so measure it into your space before ordering. The G-Tools silencer slides onto the outlet of the 125 mm GT fans and is meant for those fans.

Or a fan that is already damped

The Can-Fan Iso-Max sits in an insulated jacket and solves the problem at source, in Ø150 at 410, Ø160 at 430, Ø200 at 870 and Ø250 at 1480 cubic metres per hour. Watch out if you plan to throttle it: the smaller versions have three built-in speeds and must not be given an external speed controller, while the Ø250 has a single fixed speed and may be controlled. More on that with the inline fans.

All in one

The G-Tools mini fan with filter and silencer combines fan, carbon filter and damping in one housing, the simplest answer for a grow cabinet or small tent. The same idea at a larger scale sits under extractor fans, where the fan already lives inside a damped enclosure.

Frequently asked questions

Before or after the fan?
After is usual, because that is where air speed is highest. The intake side also works and helps against noise radiating into your tent. Space usually decides it.

My duct is quiet but I still hear the fan. How?
You are hearing structure-borne noise: the vibration runs through the mounting or the duct into your frame, which radiates it. Hang the fan loose or fit a rubber sleeve.

What length of silencer do I need?
Longer damps more, so the longest that fits. Measure the space left in your run first, because a silencer that does not fit is the commonest wasted purchase here.

Is a damped fan better than a separate silencer?
If you are still buying, yes, because it saves a part and a connection. If you already own a fan, a separate silencer is the cheaper route.