Industries
Energy infrastructure acoustics and noise assessment
Energy projects are approved through a technical process and opposed through a political one. Noise sits in both. It is a real constraint that the ministry assesses against published limits, and it is also the ground on which objections get made, which means the acoustic assessment gets read far more widely than it was written for.
It is also a genuinely tight technical problem. Most of this infrastructure goes in rural areas where the sound level limits are lower, the evening limit starts earlier, and the equipment runs continuously through the night.
Our experience
The engineers at Bentham have worked as acoustical consultants on energy projects across Canada: battery energy storage, solar generation, transmission and distribution stations, natural gas peaking plants, and distributed generation deployed across whole portfolios of sites.
Much of that has been noise control engineering rather than assessment alone. One programme deployed dozens of megawatt-class peak-shaving generators across Ontario, many on retail sites backing onto homes. The enclosure design covered acoustically treated housings, silenced intake and discharge, and very high attenuation exhaust mufflers. The enclosure was standardised across the fleet, with a site-specific assessment at each location, and approvals came through across the programme without redesigning site by site.
Measurement is the other half of it. Refurbishments at transmission and distribution stations across Ontario each needed permitting support, across transformers of many sizes and models. Where the number had to be right, sound intensity measurements isolated an individual transformer’s sound power while other equipment and background noise were running. Approvals were obtained across the programme.
Timing is what makes these facilities contentious. Peaking plants run when the grid is under strain, which often falls in the evening, when the limit has dropped and neighbours expect quiet. On several natural gas peaking plants in Ontario the assessment was made against that condition rather than an average one, and the approvals were granted. Where a project has been opposed, the engineers at Bentham have given expert evidence for proponents and objecting parties alike.
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
Rural limits are the tight ones.
A Class 3 area carries a 45 dBA daytime limit and 40 dBA from 19:00, which is five decibels tighter than urban and applies for a longer part of the day. Facilities are sited in rural areas precisely because there is nobody nearby, and then assessed against the strictest limits in the guideline for exactly the same reason.
Transformers and inverters are tonal.
The hum from transformer cores and the switching noise from inverters concentrate energy at specific frequencies. Tonal sound attracts an adjustment under NPC-300, so a facility can sit below the overall limit and still fail. It is also what makes this equipment audible at distance and recognisable when it is, which is a different problem from being loud.
The receptor may not be built yet.
NPC-300 requires assessment against hypothetical points of reception on vacant land that could support a sensitive use, and agricultural parcels generally permit a dwelling. On a rural site the governing receptor is frequently a house that nobody has built.
Supplier sound data is the weak link.
Manufacturer data for containerised battery units, inverters and transformers varies widely in quality and is often given without the operating condition it applies to. Where the assessment depends on it, the right move is to measure the equipment or to write the sound performance into the supply specification, before the order is placed.
How the mitigation is worded decides what the site can do.
An approval condition naming a specific barrier locks the facility into it. Written as a performance requirement, the same condition can be met through equipment selection, layout, enclosure, orientation or operating limits, and it can be revisited as the technology changes across the life of the facility.
When a project is opposed
Energy infrastructure in rural municipalities draws organised opposition, and noise is one of the grounds most often raised. The assessment will be read by councillors, by residents, and sometimes by another acoustical consultant retained to review it.
That is a documentation problem as much as a technical one. Assumptions stated plainly, source data identified and justified, worst-case operating scenarios shown to have been considered, and the mitigation explained in terms a non-technical reader can follow. An assessment written only for the ministry reviewer will be quoted back selectively by everyone else.
Where a matter proceeds to a hearing, the engineers at Bentham have given expert evidence and acted for both proponents and objecting parties.
Standards and requirements in Ontario
Battery storage and most generation and transformation facilities are assessed as stationary sources under MECP publication NPC-300, which sets the sound level limits by area class and the assessment methodology. There is no acoustic regulation specific to battery storage.
Approval is generally through registration on the Environmental Activity and Sector Registry or through an Environmental Compliance Approval, depending on the facility. The acoustic assessment report is a required part of either. Sound level limits apply individually to each facility, which matters where several projects cluster on the same corridor, and NPC-300 requires the assessment to reflect the predictable worst case rather than typical operation. Municipal zoning, site plan conditions and noise by-laws apply on top, and construction noise and vibration is usually addressed separately.