redacted title [Noise cancelling towers]

How do they work?

I am using tons of these towers, yet I am flooded with enemies and the map shows that my base is all purple (from production), even outside the walls.

If i click on the tower shows a percentage (mostly 6%). How this effects the cancelling and how to raise it to 100%?

Thank you

Put a wall around your base. Add noise canceling towers where that's not enough (especially along seas) and next to the rocket silos. Use the slowest belts that do the job. Belts are loud in large numbers and high speeds.

NC towers reduce noise constantly as long as they are powered.