After less than 1/100
th
of a second, the room has
developed a complex wave pattern with energy varying
with room position. The listener is now awash in a series of
wave-fronts which will soon reflect off the wall behind.
A mere 5 milliseconds later, the initial direct wave-front
has now reflected off the rear wall and has made its way
back to the listener.
The listener will perceive this reflection as additional bass
energy, though a standing wave has not had time to
develop.
It is a common misconception that such low frequency
excess energy is merely the result of inevitable resonances
within the room, when a large portion can be attributed to
initial reflections.