New device for measuring sound scattering coefficient of vertical facings present in industrial rooms.

Wall facings present in workshops often have a relief which scatters the propagating sound waves. Predictive software tools for mapping the acoustic pressure field at workplace need acoustic characteristics such as the absorption or diffusion of scattering wall facings. In this work, we have validated a new measurement system for determining in situ sound scattering coefficients of vertical walls. The measurement device originally operating in free-field conditions has been adapted to overcome problems of parasite echoes coming from reverberation of the other inner-walls of the building and from noisy sources present on the site. To allow spatial filtering and time separation of these parasite echoes, an acoustic array using multipolar weighting and an impulsive sound source have been used in a first experimental system which was used for studying sound scattering mechanisms of horizontal facings (floor-standing). The new device improved by better synchronization of reflected echoes in the averaging process has been validated by studying the results reproducibility on site. A larger multipolar array has been implanted to involve most accurate results at low frequencies. Measurements of sound scattering coefficient of a vertical facing containing rectangular cavities have been carried out for several incidence angles in a reverberant and noisy room. These measures allowed to draw sound scattering coefficient maps along vertical directions and thus to show that the sound scattering mechanisms vary according to the measuring point. These maps can be compared with calculations using a model previously developed.