Noise Reduction Calculator Formula

Understand the math behind the noise reduction calculator. Each variable explained with a worked example.

Use the Noise Reduction Calculator

Formulas Used

Combined Noise Level

combined = 10 * log10(pow(10, source1/10) + pow(10, source2/10))

After Barrier Reduction

after_barrier = 10 * log10(pow(10, source1/10) + pow(10, source2/10)) - barrier_reduction

Variables

VariableDescriptionDefault
source1Sound Source 1 Level(dB)85
source2Sound Source 2 Level(dB)82
barrier_reductionBarrier Insertion Loss(dB)10

How It Works

Combining Sound Levels

Sound levels in decibels are logarithmic, so they cannot simply be added.

Formula

L_total = 10 log10(10^(L1/10) + 10^(L2/10))

This converts each level to linear power, sums them, and converts back. Two equal sources produce a combined level 3 dB higher than either alone (not double). A noise barrier reduces the combined level by its insertion loss.

Worked Example

Two machines at 85 dB and 82 dB with a 10 dB barrier.

source1 = 85source2 = 82barrier_reduction = 10
  1. 0110^(85/10) = 316,227,766
  2. 0210^(82/10) = 158,489,319
  3. 03Sum = 474,717,085
  4. 04L_total = 10 x log10(474,717,085) = 86.7 dB
  5. 05After 10 dB barrier: 86.7 - 10 = 76.7 dB

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