Of course, if a reasonably accurate estimate of power required for a given sound level is to be made, "reflections, etc" shouldn't be neglected, since they significantly add to the sound level and reduce the calculated power required(compared to the simple 6dB loss per doubling of distance assumption). Methods of calculating this differ, but about a year ago when a lengthy power analysis was made here by Gena et al, I cited Linkwitz, especially
this section , showing a method and example of how to take into account room factors.
