ᐅ Sizing of the Silencer (Helios Controlled Residential Ventilation EC 370)

How important is the length of the silencer in the ventilation system?

Helios sells flexible duct silencers with a length of 1000 mm (39 inches) and recommends using them without shortening. In practice, however, the silencers are often cut down because the required installation space is not available. Helios considers this a common compromise but does not specify minimum lengths for effective sound attenuation.

How do you evaluate the lengths of silencers?

How long is your silencer? Are you satisfied with the noise reduction?

We have a Helios controlled residential ventilation system EC 370. Our silencer is shortened to 420 mm (17 inches) and we are dissatisfied with the noise levels.

Hello,

420 mm (16.5 inches) seems very short to me. We have silencers installed that are 1000 mm (39 inches) long, plus additional silencers in front of the outlets in all bedrooms.

That is fine. However, at full power the system can already be heard quite slightly.

jx7 schrieb:
In practice, silencers are often shortened because the necessary installation space is not available.

Then the designer dropped the ball and planned the system incorrectly. They should have made sure the installation space was available.

Best regards,

Andreas

For silencers, the sound reduction is proportional to their length. Assuming the silencer provides an insertion loss of 10 dB when uncut, it would only achieve 4.2 dB at the length you specified.

This is a simplified physical approximation, but it is practically applicable. Your setup is 6 dB louder than necessary, which corresponds to the same "loudness" as four systems with the larger silencer (logarithmically, doubling the sound power equals +3 dB).

Hi! Our silencer is 80cm (31.5 inches) long, and we find the sound insulation acceptable. You can only hear the ventilation system at the outlets when it is set to "party mode."

Otherwise, the device is audible only when you are in the technical room.

I have installed 1 meter (3 feet) of fresh air intake and 1 meter (3 feet) of exhaust air ducting, connected in series. For the upper floor exhaust, I added an extra 50 centimeters (20 inches) to ensure it is quiet enough...

Mycraft schrieb:
I have 1 meter (3.3 feet) of intake and 1 meter (3.3 feet) of exhaust, connected in series, plus another 50 cm (20 inches) of exhaust after that, but only for the upper floor, so it’s quiet enough...

And where is the second silencer located? How far is it from there to the outlets?