This page contains explanations specific to interference. Additionally, the metric D/U, which indicates how resistant a system is to interference, will be explained. When using two or more microphones, one must be cautious about interference.

If no interference occurs

​When interference occurs

Disturbance from unknown system

Wiretapping    ...This is not an interference problem

D/U

To indicate how resistant a system is to interference, a value called D/U is sometimes used. 
"D" represents the "d"esired signal, and "U" represents the "u"ndesired signal. D/U represents this ratio, and the unit used is dB. The video below explains D/U. Please grasp the concept.