Enter the Noise Reduction Rating (NRR) of the hearing protection and the ambient noise level to calculate the reduced noise level at the ear.

## Noise Reduction Rating Formula

The following formula is used to calculate the reduced noise level at the ear when using hearing protection with a specific NRR value.

RNL = NL - ((NRR - 7) / 2)

Variables:

- RNL is the reduced noise level at the ear (dB)
- NL is the ambient noise level (dB)
- NRR is the Noise Reduction Rating of the hearing protection (dB)

To calculate the reduced noise level at the ear, subtract the derated NRR value from the ambient noise level. The derated NRR value is obtained by subtracting 7 from the NRR and then dividing by 2, to account for real-world conditions.

## What is Noise Reduction Rating?

Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of hearing protection devices to decrease sound exposure within a given working environment. The higher the NRR number associated with a hearing protector, the greater the potential for noise reduction. However, the real-world attenuation can be less than the rated value, which is why a derating factor is applied in the calculation.

## How to Calculate Reduced Noise Level?

The following steps outline how to calculate the reduced noise level at the ear.

- First, determine the NRR value of the hearing protection (NRR) in decibels (dB).
- Next, determine the ambient noise level (NL) in decibels (dB).
- Next, gather the formula from above = RNL = NL – ((NRR – 7) / 2).
- Finally, calculate the reduced noise level (RNL) at the ear in decibels (dB).
- After inserting the variables 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.

NRR value of the hearing protection (NRR) = 33 dB

ambient noise level (NL) = 100 dB