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The noise impact of a cup of tea
It’s a quirky English phenomenon that, during advert breaks for Coronation Street or Eastenders, a large proportion of the country decides to make a cup of tea.
It’s a race against time – you have around 3 minutes to boil the kettle, suitably stew the tea bag, add the milk (do you take sugar?) and get back to the settee in time to ensure you don’t miss the next plot twist.
Kettle manufacturers are conscious of this predicament, with kettles being designed to boil water as quickly as possible. Most UK kettles draw 3Kw, which is at the limit of what domestic plugs can handle and roughly the electricity generated by 21m2 solar panels in full sunlight.
With approximately 1.5-1.75 million kettles being boiled during any single advert break – this needs a lot of power!
This puts a huge and sudden demand on the national power grid that the larger power stations can sometimes struggle to meet. In fact, national grid employees watch TV to help them prepare for the surges as best they can, as shown in this recent documentary.
To help solve this problem at a local level, a number of smaller and more reactive biodiesel and gas power generation sites are increasingly being installed around the country. These facilities can ramp up quickly as required to support the power supply in a given area; a flexible solution to a very British problem!
One potential drawback of these systems is the noise output from their generators – which can be significant. Careful acoustic design and planning is therefore crucial to ensure that nearby residents are not disturbed and applications for new sites run smoothly.
Based on our experience, we have put together a list of factors that are important in the successful implementation of these sites.
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Location
Urban and rural sites present different challenges. Background noise levels tend to be higher in urban areas than in rural areas, which means that the noise from the generators will be less audible in urban areas. However, it is likely that people will be living closer to the generators. Conversely, rural generator sites tend to be situated farther from residents, but background noise levels can be extremely low meaning that generator noise can be heard over a larger distance.
The generators should always be placed as far as possible from residents; however other noise mitigation strategies are often also helpful.
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Barriers
Acoustic fences or bunds can be effective in reducing noise from the site. In general terms, the closer and higher the barrier is to the equipment, the more effective it will be. Additionally the design of the barrier (e.g. surface mass, number of gaps etc.) will also play a large part in the overall effectiveness.
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Selection of Units
It is recognised by the industry that the generators can be noisy. As such it is common for manufacturers to provide ‘low noise’ models or acoustic enclosures. Our experience is that, wherever feasible, this should be allowed for at the outset of the project given the nature of the noise and typical locations of the sites.
Additionally, the more detailed the noise data provided by the manufacturers, the more accurate acoustic calculations can be. With detailed noise data we are able to carry out a value engineering exercise and explore using fewer or smaller barriers for example, whereas this may not be possible with only basic noise data.
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Local Planning Authority Consultation
Typically, the generators run sporadically and for only short periods. As such, stringent mechanical plant noise limits, which would be appropriate for more constantly running plant, are often not applicable for these sites. This means that design targets may potentially be relaxed, which would reduce the amount of physical noise mitigation required. It is important that the LPA are consulted as early as possible by a competent acoustician to negotiate the possibility of a relaxation to the design targets.
Through appropriate calculations and 3D noise modelling, Cass Allen are able to advise on the feasibility of new schemes, optimise site layouts and design the size and location of noise barriers and other mitigation measures where required. In this way, we can help keep the noise impact of your cup of tea to a minimum.
