R&D Report 1992-11 : A modular wideband sound absorber G.D. Plumb The absorption coefficients were measured of various depths of RW2 grade Rockwool laid directly on the floor of the ISO-Standard reverberation room at BBC Research Department. The Rockwool was very effective as a wideband sound absorber. A new absorber was designed and tested, having the dimensions of existing BBC type A modular absorbers and containing RW2 Rockwool. The new absorber has a smoother absorption coefficient curve, a less complicated construction and weighs less than the existing BBC wideband absorber (type A8/A9). It has been named type A11 and has an equivalent performance to that of BBC type A2 and A3 absorbers combined. It complements, very well, the performance of the A10 very low frequency absorber, described in a companion Report (BBC RD 1992/10).