Calculate noise reduction coefficient, composite NRC, sabins, and RT60 from band absorption values, room size, panel area, and count.

NRC describes absorption, not sound blocking. Laboratory coefficients may exceed 1. Room and composite outputs are estimates; mounting and sound-field conditions matter.

Absorption-area estimate

This cap affects the area estimate only; it does not change NRC.

Related Calculators

Noise Reduction Coefficient Formula

The following formula is used to calculate the Noise Reduction Coefficient (NRC) for given absorption coefficients at different frequencies.

NRC = roundโ‚œoโ‚™earestโ‚€.05((ฮฑโ‚ + ฮฑโ‚‚ + ฮฑโ‚ƒ + ฮฑโ‚„) / 4)

Variables:

  • NRC is the Noise Reduction Coefficient
  • ฮฑโ‚ is the absorption coefficient at 250 Hz
  • ฮฑโ‚‚ is the absorption coefficient at 500 Hz
  • ฮฑโ‚ƒ is the absorption coefficient at 1000 Hz
  • ฮฑโ‚„ is the absorption coefficient at 2000 Hz

To calculate the Noise Reduction Coefficient, sum the absorption coefficients at 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz, then divide the result by 4 and round the mean to the nearest 0.05.

What is a Noise Reduction Coefficient?

The Noise Reduction Coefficient (NRC) is a scalar representation of the amount of sound energy absorbed upon striking a particular surface. It is an average rating of how much sound an acoustic product can absorb. NRC rates sound absorption rather than sound blocking or transmission loss. Higher values indicate greater measured absorption over these four bands; mounting and test conditions matter. It is particularly useful in environments where controlling noise levels is crucial, such as recording studios, theaters, and offices.

How to Calculate Noise Reduction Coefficient?

The following steps outline how to calculate the Noise Reduction Coefficient (NRC).

  1. First, measure the absorption coefficient at 250 Hz (ฮฑโ‚).
  2. Next, measure the absorption coefficient at 500 Hz (ฮฑโ‚‚).
  3. Then, measure the absorption coefficient at 1000 Hz (ฮฑโ‚ƒ).
  4. Finally, measure the absorption coefficient at 2000 Hz (ฮฑโ‚„).
  5. Calculate the NRC using the formula: NRC = round_to_nearest_0.05((ฮฑโ‚ + ฮฑโ‚‚ + ฮฑโ‚ƒ + ฮฑโ‚„) / 4).
  6. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Absorption Coefficient at 250 Hz (ฮฑโ‚) = 0.5

Absorption Coefficient at 500 Hz (ฮฑโ‚‚) = 0.6

Absorption Coefficient at 1000 Hz (ฮฑโ‚ƒ) = 0.7

Absorption Coefficient at 2000 Hz (ฮฑโ‚„) = 0.8