Noise Reduction Calculator Formula

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

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Formulas Used

Noise Reduction

noise_reduction = transmission_loss + 10 * log10(receiver_absorption / wall_area)

Variables

VariableDescriptionDefault
transmission_lossTransmission Loss (TL)(dB)45
wall_areaPartition Area(m2)15
receiver_absorptionReceiving Room Absorption(m2 Sabine)30

How It Works

Noise Reduction Between Rooms

The noise reduction (NR) is the actual level difference between two rooms separated by a partition.

Formula

NR = TL + 10 log10(A / S)

  • *TL* = sound transmission loss of the wall (dB)
  • *A* = total absorption in the receiving room (Sabine)
  • *S* = area of the partition

    • If the receiving room is very absorbent (A > S), NR exceeds TL. If it is reverberant (A < S), NR is less than TL.

    Worked Example

    Wall TL = 45 dB, wall area = 15 m2, receiving room absorption = 30 m2 Sabine.

    transmission_loss = 45wall_area = 15receiver_absorption = 30
    1. 01NR = TL + 10 log10(A/S)
    2. 02NR = 45 + 10 log10(30/15)
    3. 03NR = 45 + 10 log10(2)
    4. 04NR = 45 + 3.01 = 48.01 dB

    Frequently Asked Questions

    What is transmission loss?

    TL measures how well a partition blocks sound. It is the ratio of incident to transmitted power in dB. A concrete wall might have TL = 50 dB; a thin plasterboard wall about 25 dB.

    Why does receiving room absorption matter?

    Sound that enters the receiving room reverberates. More absorption means the energy dissipates quickly, lowering the steady-state level and increasing effective NR.

    How do I improve noise reduction?

    Increase the wall TL (thicker, denser, or double-leaf walls) and increase absorption in the receiving room (acoustic panels, carpet).

    Ready to run the numbers?

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