Air_US_rev_111.qxd
ACOUSTICS - BACKGROUND INFO
At low frequencies a monitor can be considered as to radiate the sound energy in all directions.
This is also called a 4 π radiation.
When placing the monitor close to a solid boundary - for instance a wall - the sound energy that should have been radiated in the direction of the wall instead is radiated into the free half space. Hence the sound pressure is doubled in the half space, which yields +6 dB.
This is also called a 2 π radiation.
Placing the monitor against two boundaries - for instance in a corner limited by two walls - it is now radiating to the quarter space. Now the sound pressure is doubled twice, which yields +12 dB.
This is also called a π radiation.
Placing the monitor against three boundaries - for instance in a corner limited by the floor and two walls - the sound is radiated into 1/8 of the space. Compared to free space, the sound pressure now is increased by 18 dB.
This is also called π/2 radiation.
In practice the placement close to boundaries will influence the frequency range below
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