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Eliminating flanking

Flanking sound is transmitted indirectly via paths such as external wall cavities, voids above partitions and internal corridors. If the wall/floor/partition concerned has good sound reducing capabilities then the sound will try to find the easiest way of getting from A to B. In short if it can’t go through the wall it will go up and over or around the side. It is imperative that flanking transmission is considered at the design stage and that the construction detailing specified will eliminate or at least minimise any downgrading of the acoustic performance.

To assist the designer, good practice detailing at key junctions is provided throughout Approved Document E. Solutions are presented showing the essential gap filling, joint sealing, fire-stopping, cavity closing and continuity of insulation to prevent sound transmission through critical junctions.

In a 2009 survey of local authorities in England carried out for the National Deaf Children’s Society, only one in five respondents had new schools with acoustics meeting DCSF requirements in BB93. ‘Grand Designs’ presenter Kevin McCloud called for improvement:

“… organising the acoustics of teaching spaces to help the hard of hearing or profoundly deaf is a precise science and more can be done to make the learning life easier for those affected. The technologies exist: hearing loops can be put in; materials science for ceiling boards, insulation and cladding is advanced; a lot of solutions can be retrofitted even. The knowledge is there.”