Sonodec 203 mm 3 meter

Acoustically insulated ducting from DEC International in 203 mm, three metres long. For systems with a 200 mm connection.

Length is the dial you turn here

For most parts of a ventilation system the size decides what it does. For acoustic ducting it is the length, and the effect is larger than you would expect.

DEC's measured values for this diameter show it directly. At 1000 Hz, roughly where a fan's hum sits, this ducting attenuates 20 dB over one metre, 35 dB over two and 41 dB over three. The step from one to two metres therefore delivers nearly as much again as the first metre did, and only after that does the gain flatten off.

That makes the choice simple: one metre of acoustic ducting is a half measure. For a noticeable effect, three metres is the length at which the material reaches its published values, and that is exactly what you are buying here.

It works the other way too. If you have only a metre between fan and outlet, a short acoustic length is not the answer and you are better off looking at a silencer or a different layout.

Technical Specifications:

• Brand: DEC International, Sonodec
• Construction: perforated aluminium laminate inner hose with barrier and laminate sleeve
• Insulation: 25 mm glass wool
• Bend radius: 0.54 times the diameter plus 25 mm
• Air speed: maximum 30 m per second
• Diameter: 203 mm
• Length: 3 metres

Frequently asked questions

Can I put two lengths in series for more damping?
You can, but the manufacturer publishes no values above three metres, so we promise no extra gain there.

Where should those three metres go?
Directly behind the fan, since that is where the noise is strongest.

Does it work on the intake?
Yes. If you run an intake fan, the same story applies there.