Gain-Change Formulas

Formulas based on microphone placement and the number of open microphones.

Mic Placement Formula:

                 Distance Old
20 x log (     ------------     )
                Distance New

Example: How much will the gain of the sound system increase if mic is moved from 12 inches from talker to 3 inches from talker?

12/3 = 4
log 4 = 0.6
0.6 x 20 = 12 dB of gain increase

Number of Open Mics Formula:

                 NumberOpenMicsOld
10 x log (    -------------------------     )
                NumberOpenMicsNew

Example: How much will the gain of the sound system decrease if the number of open mics goes from 4 to 9?

4/9 = 0.44
log 0.44 = - 0.35
-0.35 x 10 = -3.5 dB of gain change

revised: 2/5/2007