This ensure a 12db level difference between adjacent microphones and thus eliminates phase cancellation distortion problems.
If two microphones are picking up the same sound source from different locations, some phase cancellation or summing may be occurring.
Phase cancellation happens when two microphones are receiving the same soundwave but with opposite pressure zones (that is,180 degrees out of phase).
microphones
The areas coloured above will suffer degradation due to the soundwaves being out of phase.The solution is to have the microphones spaced wider, or closer to the sound source depending on what is most practical for the circumstances.
