Data Centre Noise Control
As our reliance on IT and web-based cloud computing continues to rise, the infrastructure to support this growing trend needs to be equally as cutting-edge and efficient. Data centres, whilst housing some of the most advanced computer processing technology, can also generate large amounts of noise if not controlled appropriately.
There are typically 5 key sources of noise associated with data centre operations, these usually take the form of: back-up generator plant rooms, roof-top air handling equipment, external machinery compounds, perimeter screening and the data halls themselves.
Gaining the correct balance between airflow and attenuation is key when designing a plant room, especially if it is housing back-up generators. Generators, when operating, are usually the noisiest pieces of equipment in any data centre. Due to their key function of keeping the site running should a power failure occur, the level of attenuation required needs to cater for the quietest ambient times of day – typically during the night.
Sometimes required to run for extended periods of time, plant rooms housing any live generators need to be suitably designed to ensure the correct and efficient airflow, whilst maintaining an agreed acoustic specification. Any attenuation required on both the intake and exhaust need to be designed prior to building. Sufficient space needs to be given for silencers, especially if the acoustic specification is high to avoid larger openings or additional external silencers being added.
The construction of the room itself also needs considering to reduce noise break-out to adjoining rooms within the centre. Typically block work or concrete is used to create mass and hence reduce noise transmitted however weight is a huge factor to consider, especially for rooms located above ground level. Acoustic panels can be used in this instance as a lightweight solution to reducing noise and depending on the configuration, shorten reverberation times within the room. By increasing the amount of absorption within the room, this has the effect of further reducing noise. Absorption can also be added to rooms constructed in traditional materials by lining the walls and ceiling with rugged acoustic panels.
Access also needs consideration as these are typically areas of weakness in the acoustic integrity of a plant room. Specialist acoustic doors may be required depending on the level of attenuation required and their proximity to quieter areas of the facility such as offices.
Roof-top Mechanical Equipment
Due to the large volumes of conditioned air required to cool data centre halls, mechanical plant such as chillers are usually located at roof level. Screening noise can be a challenge, especially if the centre is located amongst other high-rise buildings. Constant airflow ensures the equipment can run efficiently, but this can cause issues with noise. Acoustic louvres are typically used to minimise noise levels, whilst maximising airflow to the equipment.
Where airflow is less of an issue, acoustic barriers and fan mounted silencers can also be used to further reduce noise if required.
External Mechanical Plant Compounds
External compounds located at ground level typically need additional attenuation in the form of barriers and screens, depending on their location within the perimeter of the site. Acoustic mapping is usually carried out as part of the design process to optimise the position of a compound to maximise attenuation. By placing a compound as far away as possible from potential receptors (usually nearby residents), this will improve the levels of noise emitted and reduce the need for specialist attenuation.
When required, there are a number of products that can be used either as standalone solutions, or as part of a complete package. Depending on the equipment requiring treatment, acoustic louvres, enclosures, barriers and containers can all be used to reduce noise.
If targeted treatment of individual noisy elements is not enough, or not financially viable, then screening parts (or sometimes all) of a data centre can help to reduce noise in certain directions. With varying performance levels and many different materials available, the most important factor to consider is the long term performance of the barrier. Metal / composite barriers tend to be the hardest wearing against the elements. As these materials are less prone to warping / cracking, their acoustic integrity is maintained for the lifetime of the barrier.
Noise within the data halls can be high if not properly treated. Despite the fact that many data centres operate with little or no personnel, people are however required to do physical maintenance and repairs on individual servers. If people are required to work in the halls for any length of time, then the ambient background noise levels should be low enough to meet local regulations.
Typically it is the air handling system which is the primary source of noise within the server halls with large volumes of conditioned air being passed into and out of the racks 24/7. Sufficient levels of attenuation are required to limit the noise entering the halls. In addition to treating the airborne noise entering the halls, a degree of isolation may also be required to shield the area from adjoining spaces. Acoustic doors and acoustic windows can be used to provide additional screening at access points which without treatment can be weak points for noise to escape.