Directional Distribution of Reflections in Home Cinemas - November 12th, 2008
Let’s take into consideration a property which characterises a reflection, namely the direction from which it reaches an observer at the home cinema seating area. We shall not attribute to each single reflection its proper direction, but we shall apply a summarising method, which commends itself not only because of the great number of reflections making up the resulting sound field in a dedicated home cinema room, but also because we are usually not able to locate subjectively the directions from which reflected and hence delayed components reach our ears. Nevertheless, whether the reflected components arrive uniformly from all directions or whether they all come from one single direction has considerable bearing on the acoustical properties of home cinema installations. The directional distribution of sound is also important for certain measuring techniques.
In a certain sense, the diffuse sound field in a home cinema room is the counterpart of a plane wave. Just as certain properties can be attributed to plane waves, so relationships describing the properties of diffuse sound can be established. They are of particular interest to the whole of home cinema acoustics, since, although the sound field in a home cinema is not completely diffuse, its directional structure resembles much more than that of a plane wave. Or, put in another way, the sound field in an actual home cinema design, which always contains some irregularities in shape, can be approximated fairly well by a sound field with uniform directional distribution on account of its great complexity. In contrast to this, a single plane wave is hardly ever encountered in a real situation.