hilst much of the focus on environmental noise concentrates on high noise levels emanating from vehicular traffic, construction work or even aircraft movements, the continued development of commercial and residential buildings in modern cities raises concerns with regards to the potential disruption to neighbouring properties, along with the continual rise in ambient noise across our cities.
Fixed plant items which provide heating, ventilation and power to offices, hospitals, manufacturing facilities and other commercial buildings often present additional issues with impulsive or tonal noise, which is intensifying noise pollution problems even further.
The potential negative impacts of such unwarranted noise levels should not be underestimated, especially in highly-populated urban environments. At the lower end of the scale, excessive noise emissions may be deemed as disruptive and unpleasant for nearby residents; however, they can also pose more serious health impacts.
Such is the scale of the issue, that the World Health Organisation (WHO) has described noise pollution as an underestimated threat that can cause health problems including hearing loss, cardiovascular problems, cognitive impairment, stress and depression. In addition, with the WHO stating that “one in five Europeans is regularly exposed to sound levels at night that could significantly damage health”, it is clear this is a widespread issue.
Faced with a public less tolerant of noise, and against a backdrop of increasingly stringent environmental noise targets, noise reduction has become a key focus for the construction sector, with building contractors, developers, specifiers and architects keen to address issues with excessive noise emanating from modern commercial buildings.
Within the UK, noise from fixed plant items is generally assessed through the guidelines given in BS 4142:2014 ‘Methods for rating and assessing industrial and commercial sound’. The standard is used to determine the likelihood of noise complaints from such systems and aims to quantify noise levels in relation to underlying background noise levels, during operational hours of the plant.
In the majority of cases, an assessment to BS 4142:2014 is required in order to satisfy the local planning authority that any proposals will not have an adverse effect on local residents and the surrounding environment. In instances where plant items are required to be in operation during the night, this is particularly crucial, as noise emissions are likely to be more prominent against a quieter backdrop of background noise – especially during the early hours of the morning.
Whilst the British Standard is a very useful tool for determining the potential impact from noise sources, control measures for fixed plant items can sometimes be difficult to determine, especially where high levels of noise reduction are required.
Add to this, the fact that it is common for planners to insist upon new plant installations being attenuated to noise levels as low as 10 dB below background noise, and the challenge facing today’s specifiers and building contractors becomes even greater.
Addressing excessive noise from plant items can be a complex task. Whilst full acoustic enclosures offer the best level of noise reduction; these can often be impractical in many applications given the need for high air movement for chillers, condensing units, air handling and power generation plant.
In many instances, therefore, a combination of noise control products is usually required in order to provide suitable noise reductions, as well as to ensure the required airflow to allow the plant to operate effectively. Potential noise control solutions can include acoustic panel screens with absorbent linings to the internal face, acoustic louvred screens, attenuators and acoustic enclosures, but determining the best solution, or indeed solutions, for specific applications often requires expert knowledge.
Increasingly, leading specifiers and construction companies are turning to noise control specialists, such as Wakefield Acoustics, to accurately analyse, diagnose and put in place noise control measures to address issues with excessive noise from plant items.
In one recent installation, Wakefield Acoustics was commissioned to design, supply and install a full acoustic housing for a number of externally mounted condensing units and chiller items. The client wished to reduce excessive noise originating from fixed plant items on a commercial building which was affecting nearby residents.
To effectively mitigate noise, a series of acoustic louvres were positioned around the side elevations of an acoustic enclosure which housed the plant items. The acoustic louvres contained a series of absorbent horizontal steel blades, allowing air to be drawn into the plant area whilst also reducing noise.
Efficient plant operation was an essential requirement for the project. With this in mind, a number of acoustic baffles were also installed to allow warm air from the equipment to be discharged up through the ‘roof’ of the enclosure, with separation plates to prevent air recirculation.
Due to the overall size and weight of the plant, a support steelwork structure – designed and installed by Wakefield Acoustics – was installed in conjunction with the noise control items.