Proceedings of the Institute of Acoustics Vol. 35. Pt. 2. 2013 1 IN SITU MEASUREMENT OF THE SOUND ABSORPTION CHARACTERISTICS OF EXISTING BUILDING FABRICS J. Grimes Department of Civil Engineering, Trinity College Dublin O. Kinnane TrinityHaus, Department of Civil Engineering, Trinity College Dublin R. Walker Department of Civil Engineering, Trinity College Dublin S. Pavia TrinityHaus, Department of Civil Engineering, Trinity College Dublin 2 INTRODUCTION Sound reflections from building walls may be perceived as echoes and hence can disrupt music and speech considerably. Noise due to reflection in enclosed space impacts comprehensibility of sound. Sound absorption reduces reflection from surfaces and can improve the clarity. The current standards do not outline a methodology to measure the sound absorption co- efficient, α, of wall surfaces in-situ. Instead sound absorption must be measured on a sample of wall, or wall material, in a reverberation chamber, or laboratory using an impedance tube, respectively. The easy measurement of the sound absorption co-efficient, α, is pertinent for characterisation of the noise abatement abilities of built construction. Accurate acoustic modelling of existing built spaces, and design of sound retrofit measures, are dependent on correct building material characterisation. As control of architectural materials and surfaces has improved in recent decades, architects have come to routinely specify pristine and polished surfaces. Although visually striking these lustrous surfaces promote poor acoustical performance in internal environments. Glass, smooth concrete, plastered and painted surfaces all reflect sound. Materials such as polished concrete, glass and smooth metal exhibit almost perfect reflection. In order to compensate for this absorptive panels are often specified post-occupancy by building occupants. Alternative materials could instead be specified at construction that would enable absorption of sound, particularly nuisance noise, in buildings. Soft open textures such as rock and glass wool make for good sound absorbing materials; however these do not have the strength characteristics for outer surface of walls. Instead porous concrete materials are an option. In this study a concrete with hemp aggregate, and a commercial lime-cement binder is assessed 1 . This paper presents a methodology that adapts procedures outlined in ISO-13472 2 and ISO- 10534 3 . The method was tested on a range of materials in-situ and in the laboratory. The absorption co-efficient of materials in their intended location and finish are hence determined using an impedance tube. This method provided consistent measurements, with less than 5% standard deviation. 3 RESEARCH BACKGROUND This research is concerned with the development of novel products, for internal and external, building cladding systems for new and for retro-fit buildings with the dual objectives to abate the propagation of noise and to enable energy savings in buildings through thermal insulation.