# Shure Tech Tip: Gain Changes Based on Mic Placement & Number of Open Mics

**Below is a mic placement formula from Shure Applications Engineering:
**

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

**Below is a number of open mics formula from Shure Applications Engineering:**

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