Now is an exciting time in the world of acoustics. But isn’t it always? Change is afoot. Three very important documents in the world of acoustics – particularly building acoustics – are being amended. It’s difficult to say which document is the most important, as they each consider different areas, so we’ll start with the one most recently published.
BS 8233: 2014 “Guidance on sound insulation and noise reduction in buildings” is a weighty document, and can almost be considered a handbook for acoustics in buildings. It gives criteria for internal noise levels, sound insulation and reverberation in buildings as well as a wealth of information on how to achieve the criteria. The previous version (1999) was a central document for acoustics that Local Authorities and acoustic consultants have referred to across the UK for planning conditions and acoustic criteria. The new version, which is even more expansive, will no doubt be used in the same way.
BS 4142: 2014 “Methods for rating and assessing industrial and commercial sound” is currently out for public consultation and provides a method for assessing the noise impact of industrial noise sources. The current document (published in 1997), although flawed, has been the standard reference point for Local Authorities across the UK for assessing noise from building services plant, and is referred to in planning conditions (and legal cases) across the land. The draft replacement makes recommendations for a more robust assessment method, although the new requirement for measuring weather conditions at the same time as noise measurements has already ruffled a few feathers. We hope the replacement will remove some of the ambiguity of its predecessor.
Building Bulletin 93 “Acoustic Design of Schools” was initially hailed as the answer to acoustic problems in schools (aircraft noise disrupting classes, assembly halls that echo, teachers losing their voices, etc.), intending to bring about a new era of high-performance school buildings under the intensive building programmes of the early noughties (see PFI, BSF, etc.).
However, it soon became apparent that some of the acoustic criteria contradicted other design aspirations – for instance natural ventilation – especially since BB93 required a very quiet site (most weren’t) if you wanted your school to have windows that open. Sports halls were also tricky as they generally require two sets of parallel painted blockwork walls, which don’t meet the stringent BB93 reverberation requirement. ‘Alternative Performance Standards’ were also introduced which allowed, with the right justification, a relaxation of the BB93 criteria. These were used frequently (and in many cases, wrongly) to acoustically downgrade the design (mainly to reduce cost), thereby missing the original point of BB93.
The new document (currently out for consultation) promises a more pragmatic approach, with mainly the same criteria but critically, a more sensible way of applying them, particularly for refurbishments. It’s also much clearer which buildings are covered, as this was sometimes a bit vague under BB93. All of these amendments will impact on building design and specification and may well lead to changes in planning conditions going forward. We recommend a watchful eye.
Author: Nicholas Jones, Head of Acoustics at Hilson Moran