Industries
Data centre acoustics and noise assessment
Few building types have moved from obscure to contentious as quickly as the data centre. As facilities have grown and moved closer to residential communities, noise has become one of the main issues raised in approvals, in council chambers, and by the neighbours afterward.
It is a hard problem, and it deserves to be treated as one. A large facility runs a great deal of plant continuously, including overnight, and the acoustic outcome depends on decisions made early: where equipment sits, what gets selected, how the site is laid out. Those are cheap decisions to make well and expensive ones to revisit.
Our experience
The engineers at Bentham have worked as acoustical consultants on data centre projects in Canada, the United States and Europe: acoustic assessments supporting approvals, mechanical and equipment noise control, enclosure design for cooling and standby power, and investigation work after a facility is running.
These facilities are rarely approved once. One large data centre in the Greater Toronto Area was approved in phases across half a dozen years, with the permitting and the noise control design running throughout. Because a single model carried through every phase, each change of generator or cooling selection could be tested in days, and every phase secured its approval without reopening the ones before it.
The project that taught us the most was a complaint. A large data centre adopted a novel cooling technology, and complaints followed once it was running. Our investigation found the installed fans did not perform to the sound data in the original documentation. Measuring the equipment as installed identified the sources actually driving the levels, and the remedial measures that followed brought the site back into compliance. It is why we treat manufacturer sound data as something to verify rather than rely on.
Dense sites make the physical problem harder. On a downtown refurbishment in Vancouver, rooftop chillers were overlooked by neighbouring buildings on several sides. Noise control and the airflow the chillers need pull directly against each other, and the enclosure that resolved it was built and holds both.
Bentham Acoustics is new. Its engineers are not. The projects described here were carried out by Bentham engineers over their careers, at this firm and before it.
A full list of relevant project experience is available on request.
What comes up most
Where the plant goes.
Equipment placement is usually settled by electrical routing, structural constraints and site efficiency. It is also the single biggest lever on the sound reaching a receptor, and it is the cheapest one to move while the site plan is still open.
Selection versus mitigation.
Fan and chiller selections are made against capacity, redundancy and cost. Once they are locked, the remaining options are enclosures, barriers and silencers, all of which cost more and perform less well than a different selection made earlier.
Low-frequency content.
Large fan and cooling plant produces a substantial amount of sound at low frequencies. Low-frequency sound travels further, passes through building envelopes more readily, and is not well represented by a single overall A-weighted number, which means a facility can sit within its limit and still be audible indoors at a distance. It is well documented and it is worth designing for deliberately, through selection, placement and attenuation, rather than discovering it after commissioning.
Generator testing.
Routine testing runs on a schedule that does not always align with the assumptions in an approval. It is worth settling how testing will be treated at the assessment stage rather than after the first test.
Phased buildout.
Facilities are frequently approved in phases and built over years. An assessment based on phase one has to anticipate the fully built condition, including plant added under a later approval.
The receptor that arrives later.
Sites chosen for power and land are not always sites that stay industrial. Nearby residential approvals can change the applicable limits during a project’s life.
In front of a community
Council and public meetings now ask acoustic questions directly, and reviewers, planners, councillors and residents all read this work. That changes what a good assessment looks like. It has to set out plainly what the facility will produce, where it goes, what has been done about it, and what can still be changed, in terms that survive being read out of context.
That understanding is built during design. It cannot be assembled after a question is asked, and the decisions that determine the outcome, placement, selection, orientation and layout, close in sequence. Knowing which are still open and what each is worth is more useful than a list of everything that could theoretically be done.
A facility of this size will have an acoustic presence, and pretending otherwise helps nobody. The work is to define what a reasonable outcome looks like for the site and the neighbours, and then to design to it deliberately rather than arrive at it by default. Getting that right is part of what makes a facility something a community can live alongside.
Standards and requirements in Ontario
A data centre in Ontario is a stationary noise source, assessed against the sound level limits in MECP publication NPC-300. The applicable limit depends on the acoustical class of the area around the facility and on the time of day, with the night-time period generally governing.
Depending on the facility, the noise requirement is met through an Environmental Compliance Approval or a registration under the Environmental Activity and Sector Registry, O. Reg. 1/17. Both require the sound emissions to be assessed, and the ministry provides three routes: the Primary Noise Screening Method, the Secondary Noise Screening Method, or a full Acoustic Assessment Report.
Municipal noise by-laws apply separately, and site plan and zoning approvals frequently attach their own acoustic conditions. Where a facility sits near lands being planned for residential use, the area classification itself can become a live question. NPC-300 provides for a Class 4 designation, applied by the land use planning authority to a proposed noise-sensitive development near existing industry, which shifts some of the mitigation onto the new development rather than the established facility. It is not something a data centre applies for, but it is often relevant to what happens on the other side of the fence.