‘Resistance to the Passage of Sound’

members of the Institute of Acoustics provided the necessary feed back to allow the Institute to offer a detailed technical response to Government on the proposed changes. It has been generally accepted for some time that the degree of sound insulation in dwellings in England and Wales is not high enough to provide the degree of privacy now demanded in the face of the increasing use of both domestic machinery and amplified music. The broad base of the membership provided the necessary wide view that allows the competing interests to be well represented: those who have to investigate complaints balancing their needs against those who have to advise the Construction Industry on how the improved standards are to be achieved and paid for. Following an introduction and welcome by John Seller to the venue at the Building Research Establishment the meeting Chair, Professor Bob Craik, started the meeting by making the interactive format clear. Following formal presentations form the Department of the Environment Transport and the Regions and BRE staff there would be an opportunity for members to make short presentations themselves before the open session that would bring the proceedings to a close. A number of delegates’s rose to the challenge and during the tea break forwent the refreshments to prepare their papers. The formal presentation on the detail of the proposed changes was given by Les Fothergill of the DETR who dealt with the administrative procedure including the need to consult with and gain approval from our European partners and BRAC (Building Regulations Advisory Committee). This procedure would start once the detailed comments from the IoA and other interested parties had been received and analysed and it was estimated that it would take around a year; then there would be a six-month lead in before the new regulations would apply. Members of BRE staff dealt with the technical content of the proposals that were available, in great detail. Colin Grimwood ran through the regulatory impact assessment that deals with the costs and benefits of the proposed changes. This analysed the three possible scenarios of do nothing, continue with a promotion of a best practice approach and lastly adopting the proposed changes to the building regulations. Bearing in mind that some 40% of walls and 25% of floors fail to meet the standards it was not difficult to conclude from the mass of evidence provided that the only reasonable way forward was to advance with option 3. The compliance costs were estimated at £74.5 million per annum and these were set against the benefits ranging from £24 to £240 million depending upon how the social costs were treated in the assessment. A key element of the changes was to reduce the rate of failure to less than 5% in 10 years. Matthew Ling and Carl Hopkins, both from the BRE, dealt with the detail of the changes and the ensuing consequences for the design of new buildings. The main proposal is to improve the degree of isolation both between dwellings as well as the individual rooms of them. The unit of assessment will be changed from the existing DnT,w to DnT,w+Ctr. Adding the Ctr term will have the effect of improving the isolation at lower frequencies to deal with the problems of traffic and amplified music that to date have caused so many problems. For technical reasons the actual number that appears in the regulations will be lower but it will offer a considerable subjective improvement in the degree of isolation. The improvements in airborne isolation are also supported by changes in impact sound transmission along with treatments to stairwells and other common areas of flats where noise often builds up and causes a problem. There are also a number of changes to the definitions of