Side-wall reflections aid spatial impression while front and rear early reflections do little

Evidence

Figure 7.4(b) shows that when the first reflections are added those from the side walls should contribute positively, but others from the front and rear walls appear to add little or nothing. If one is looking for places to add acoustical absorption to reduce overall reverberation time in a room, these would be good choices. Diffusers in those locations reduce the amplitude of the first reflections, but by sending energy off in other directions the reverberation time will be little changed. — Toole, Floyd E, Sound reproduction- the acoustics and…, 704