Reducing noise from HVAC, A/C, chiller, fan etc systems
In the case of open systems (i.e. where fan inlets and exhausts are not ducted), once the air noise has been reduced using either conventional silencers or new aerodynamic noise reduction technology that cuts the noise at source, then in many cases the remaining noise is dominated by vibration from fans and compressors. The best option to reduce the noise further is to damp key system elements. In closed (fully ducted) systems damping is often a very effective option. The INVC has produced a detailed guide to noise control in chillers, air condensers and HVAC systems that includes damping to reduce noise at source.

Chiller / cooler enclosures
Fan and compressor vibration is radiated as noise by the enclosure panels. Replace with SDS or retro-damp in situ.

Ductwork
Rectangular ducting will often “pant” or vibrate. Damp to reduce the vibration and hence the noise. Quickly and easily retro-fitted without the issues associated with conventional lagging (maintenance and corrosion).

Fan motor mounts and plinths
These are often constructed from large, flat steel sheets that behave as very efficient loudspeakers. Simply add SDS retro-damp dampers to cover most of the flat areas to reduce the noise radiated by these components by 10dB or more. This can also be an effective noise control treatment for fan volutes.