Noisy HVAC systems need the silent treatment

Noise is all around us and can interfere with our working efficiency by being an annoyance and causing stress. Good or bad, the acoustical environment in buildings is ultimately a result of design and so it's never been more important for architects and building engineers to silence a well-known source of undesirable noise and vibration – heating, ventilation and air conditioning systems.

A fundamental element of buildings across a wide range of sectors, building services equipment can create unwanted noise problems leading to workplaces that are uncomfortable and less productive. Noise sources can include everything from fans to variable air volume systems; grilles and diffusers to roof-top units; fan coil units to chillers, compressors and condensers; pumps and stand-by generators; boilers and cooling towers.

As we create more energy efficient and airtight buildings, this has a knock-on impact both thermally and acoustically. However, this further drives the need for ventilation and thermal management, and this required airflow can then introduce a noise issue of its own, both break-out and in-line noise.

Break-out noise is where sound transmits through the wall of ducting and into the room through which the ductwork is travelling.  In-line (duct-borne) noise or noise traveling through ductwork can create unwelcome high levels of background noise if not properly managed. This noise can raise stress levels in the workplace, harming communication and concentration and increasing fatigue. A poorly designed acoustic solution can potentially exacerbate issues by causing regenerative noise, and negatively affecting airflow. There's also the issue of cross-talk, whereby speech privacy is compromised by room-to-room transmission via the ventilation system.

Air velocity within a duct system is another important element as it influences the noise levels significantly. Regenerated noise can be created by transition pieces, bends, dampers, grilles and diffusers. Regenerated noise can be reduced by limiting the air velocities within the duct system; by easing transitions in the system design and by ensuring that internal acoustic treatments contain chamfers where appropriate to reduce the turbulent effect of sudden changes in opening or direction.

When two adjacent or closely positioned rooms are sharing the same ductwork, sound travels within ducts and will decrease the room-to-room sound insulation dramatically. This, will of, course impact speech privacy and negatively affect the working environment through disturbance.

Vibration and sound energy from HVAC operation will transmit to a structure and be redistributed around a building.  By isolating your systems from the structure before it has a chance to vibrate, through isolation mounts or decoupled through flexible linkages from the structure via the noise source and the duct runs, another path of noise has been reduced through physical materials.

Silent treatment

The SIDERISE range of noise control solutions can be tailored to meet project -specific design and performance requirements such as the octave band requirements of your HVAC unit, thereby delivering the optimum acoustic performance at the minimum cost. Manufactured from high performance open cell acoustic foam, parts are designed to ease airflow and lower regenerative noise, and the lining treatment is engineered to deliver the lowest possible Sound Power (LwA). These acoustic solutions give exceptional noise absorption, yielding reduced airborne noise at inlets and outlets, and lowering case radiated noise.  Lining kits are Class 0 fire rated to EN 13501-1 to comply with Building Regulations Approved Document B.

Supplied as an easy-to-fit, pre-cut kit and backed with high performance modified acrylic adhesive for rapid installation on a manufacturer's assembly-line, these noise control solutions offer exceptional performance for fan coil units, air handling units and heat exchangers.

Existing buildings can benefit too. If there is a ductwork ‘in-line' noise problem, open-cell melamine resin foams are an easy and cost-efficient way to introduce noise control.  At the terminal ends, where air is being delivered to the occupied spaces, you can remove the grille and simply install the foam inserts. Inherently flexible, the inserts are ideally suited to retro-fit installation, particularly in situations where there is minimal access and/or where less disruption is a consideration.  For ‘duct noise breakout' another solution, which contributes well to quiet air-handling, are externally applied acoustic treatments. Easy to install without disturbing the HVAC system, this solution reduces break-out noise by providing a combination of acoustic absorption and sound reduction via inherently damped flexible mass membrane.

While it's difficult to escape sound completely, by proactively considering potential acoustic problems at the design stage of a HVAC system and adding sound control measures to minimise unwanted noise, building owners will have a far quieter system, which in the end, can go a long way towards promoting comfort and productivity.  

By Graham Laws – Business Development Officer, Siderise

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