Scattering by a barrier in a room

In this paper, the prediction of the effect of a simple scattering element on the acoustics of a room is studied. For the sake of simplicity, the room is a rectangular one with hard walls, and the scattering element is a horizontal thin hard strip-like barrier placed at one or two side walls. The diffraction model adopted for the sharp edge of the scattering hard strip is an exact one based on geometrical optics assumptions. The impulse response of the room may be predicted through using the image sources method for the specular reflections at the hard walls and the barrier in combination with the diffraction model which is expressed in the time domain. From the impulse response many room acoustical parameters related to the subjective rating of the room can be processed. Among these, the inter-aural cross-correlation coefficient (IACC) between two space separated impulse responses (these are usually measured at the ear entrances of a listener), which is a measure of the diffuseness of the field, can thus be calculated at different positions in the room. Another factor, the early lateral energy fraction (ELEF) can also be calculated. Some experimental results on the measurement of the impulse response and of the IACC on a scale model are also presented to support the theoretical ones.