Just quickly we need to touch on this difference. The modal range obeys the rules of what we call wave acoustics. It is, pretty simply, the idea that waves stack up between room boundaries of comparable size, and make resonances. Also, when the sound encounters an obstacle of less than comparable size, it will simply 'flow' around it. Comparable in this case means equal to, or larger than half a wavelength.
Ray acoustics predominates in the Specular range. Here we use the simple rule that the angle of incidence is equal to the angle of reflection. We can thus use geometric solutions to calculate the path of a beam, or ray, of sound. Truly we should consider the sound to be projecting in a conical shape, covering more area as it moves outwards from the source. Clearly sound doesn't actually change it's form, but these are convenient ways of solving problems for different acoustic situations.
Wave and Ray Acoustics
Wave and Ray Acoustics
