The close proximity of the head to the rear wall has two effects. At the room boundaries (walls) the room nodes are suppressed - because the sound pressure is high
and the velocity is low. Sitting in the maximum pressure area gives the best perception of deep bass. Secondly, the reflections are shorter than the circumference of
the head, so the brain cannot measure the time delay between the ears. When the brain cannot localize reflections it ignores them. Here is a simple example of how
the brain ignores unwanted or unessential information. Imagine the situation of being in a noisy public place and conversing with the person next to you. Even though
a recording made from your listening position would sound like random noise, you can follow the conversation. If you hear your name spoken several feet away, you
can change your focus, and “listen in” on the other conversation. Our brains do this automatically all the time to, for example, filter out the annoying natural resonance
of a room to facilitate speech, or to identify potential dangers.
To sum up, it is usually best to locate the listening position so the first information to arrive at the ears is from the speaker and the secondary reflections arrive much
later and at a much lower volume. Place the listening chair near the rear wall, because the distance ( 1 to 3 feet ) is too short for the brain to measure the time delay
and locate the source of the reflection. Also, it places you at the room boundary where the perception of bass is greatest. In regards to the bass reinforcement
advantage, we will expand on that in the next section.