How Does A Duct Silencer Work?
January 9, 2020 | HVACThere are few things more annoying than trying to get to sleep in a hotel room and having to make the choice between being kept awake by noisy air conditioning or being kept awake by being too hot. Similarly, conference facilities don’t want heating, ventilation and air conditioning (HVAC) which is so loud it distracts from what the speakers have to say. There are dozens of other situations in which this kind of noise is unacceptable, and building managers have to seek a solution. Clearly, some kind of silencer is required. An HVAC duct silencer is specifically engineered to reduce airborne noise carried along ducts or produced by enclosures. You’ll also find these silencers described as sound attenuators when they are used in industrial settings.
What Causes HVAC and Industrial Noise?
The noise being conducted through ductwork and along other pipes has various causes. Sometimes equipment has been installed in too small a space, causing sound to reverberate; sometimes insecure fixings cause vibration, resulting in noise. The operation of fans to cool sensitive equipment and drops in air pressure can all cause noise, as can the operation of equipment being used on a factory floor. So before installing duct silencers or sound traps, the cause of the noise has to be investigated because the solution differs according to the cause of the problem. A system survey can establish how the noise is being generated and which pipes or openings are transporting it through the building.
Where equipment used in industrial applications produces a lot of noise, it’s possible to install a sound trap to contain it. Combined with a duct silencer to prevent the noise travelling, this can be very effective at reducing noise.
HVAC Attenuators Won’t Work in Isolation
An HVAC silencer has to be part of a “whole system” approach to noise reduction, because piecemeal measures are unlikely to work on their own. Silencers are available in both cylindrical form to fit ducting and rectangular form to fit over or around noisy HVAC equipment, and in large industrial or commercial applications, banks of HVAC attenuators may be used.
When sound waves meet the HVAC attenuator, the perforations inside it allow the waves to fill the acoustic media inside the fitting. This acoustic media or “baffle” is usually composed of millions of tiny air pockets but can also be fibre. Its thickness varies according to the frequency of the sound being controlled. Low-frequency silencers are engineered specifically for 63Hz and similar octave bands.
A duct silencer can be engineered specifically for use in clean environments, such as hospitals. The linings in the silencer don’t shed particles into the air. But it’s also possible to have silencers that don’t have any filling. They are therefore much easier to clean, so these are suitable not only for hygienic environments but also for places such as chemical plants, where hazardous, flammable or corrosive matter may be present in the environment. HVAC engineers are always happy to give advice on the most appropriate silencers for your application.