In a church setting, I'm having problems with mics being used for various parts of the service and then being left open, creating feedback problems. Is there a product with some sort of proximity sensor that could turn the mic off when the speaker steps away from the podium?
Use a voice activated mixer like the Shure SCM810 or SCM820.
To calculate the increase in gain if the unused mics are off, use this formula:
10*log(number of open mics). Here is an example for 6 open mics:
The log of 6 is 0.778.
0.778 times 10 = 7.782 = rounded to 8
Having 1 mic open instead of 6 mics open with be 8 dB louder.