HVAC and LEV noise and vibration attenuation

In a surprising number of cases, although you might assume that the noise from HVAC and other fan systems is always dominated by airborne sound, structural vibration from panels, frame or other elements can be major noise contributors. Where this is the case, sound damped steel or aluminium can provide a very simple and low-cost solution – either by replacing panels with highly damped, laminated metal versions or by using our retro-fit kits to damp existing elements. This is a rugged solution that has no effect on performance, access or maintenance.

Chiller or cooler noise reduction is a classic example. Fan motor vibration is fed into thin sheet steel panels that act as loudspeakers, radiating the vibration as noise. Simply replace or laminate these panels in situ to reduce this noise component by 10dB – 20dB. In many instances, this operation can be carried out with the plant running (zero downtime). The other typical chiller noise component is compressor vibration, again transmitted into the structure and then radiated as noise. Even where the compressors are vibration isolated from the machine frame, the pipework may not be by effectively isolated. Damping the frame and panels is a very easy way to minimise this noise component.

Where the classic low-frequency tonal noise from chiller or cooler fans is the issue, then the only effective and practical solution is to use aerodynamic fan silencing technology to cut the noise at source (attenuators would often have to be too large to be practical).

On typical centrifugal fans, the noise local to the fan is often dominated by a combination of break-out noise through the fan casing and panel radiated noise from the motor plinth and/or the classic thin steel sheet shaft or coupling guard. The latter sources can be attenuated very simply by damping the panels, using our retro-damp kits to laminate in place, and replacing the guard with a sound damped steel version to reduce the radiated noise by around 10dB – 30dB.

In the former case, the fan volute break-out noise, the transmission loss of the casing can often be reduced by around 5dB via the same approach, retro-fit lamination damping. This is in addition to any source airborne fan noise reduction that may be practical.

These solutions are very widely applicable and have been used very successfully on HVAC plant, chillers, cooling towers, paint plant and many other types of fan system. They also apply to data centre noise control on cooling systems that are becoming an increasingly common cause of complaints worldwide. See examples of chiller noise control projects that include our materials