Method for measuring sound scattering coefficients of walls and diffusers by using a non-diffuse sound field with unevenly- distributed sound absorption

Method for measuring sound scattering coefficients of walls has been standardized as ISO 17497-1:2004. This standardized method employs a turntable which carries a test specimen. Due to usage of the turntable there are two limitations listed below: 1) A wall must be cut as circular shape. 2) 3-dimensional diffusers such as bent shells which are suspended from a reverberation chamber cannot be measured. Therefore we are developing a new method for measuring the sound scattering coefficient. This new method has no limitations mentioned above and can measure scattering coefficients of 3-dimensional diffusers, because the method does not employ the turntable. The method utilizes a non-diffuse sound field with unevenly-distributed sound absorption. And a sound scattering coefficient can be calculated by using a difference of reverberation decay curves between a condition with diffusers and a condition without them. Computer simulations and scale model experiments have been conducted for verification of the new method. The results showed that the new method can basically be used for measuring scattering coefficient.