Hearing Protection Calculator

Sound Level at your ear  

NRR Method Details

The NRR (Noise Reduction Rating) is a unit of measure and one of the easiest ways to assess a hearing protective device's performance and to determine its effectiveness within a given working environment to decrease noise exposure.

NRR Hearing Protection Method
The Noise Reduction Rating method follows the US OSHA method.

NRR Calculator Details
To calculate the level of exposure at the ear, first enter the NRR number as listed on the hearing protective devices box or paper work that came with the device. Next measure the worker's Noise Exposure Level in either dB(A) or dB(C). Enter the measurement into the calculator and select dB(A) or dB(C) based on the measurement method/equipment used for measuring and the result will be shown in the calculator.

Weighting	Calculation
dB(A)	Result = NL - ((NRR -7) / 2)
dB(C)	Result = NL - (NRR / 2)

Definitions 
NL is the Noise Level or Sound Level measured in either dB(A) or dB(C)
NRR is the Noise Reduction Rating in (dB) provided by the hearing protection device manufacturer

SNR Method Details:

The SNR(Single Number Rating) is a system used to determine a hearing protective device's performance and to determine its effectiveness to decrease noise exposure within a given working environment.

The Single Number Rating method is the easiest recommended method and accurate unless the noise is tonal or is dominated by low frequencies.

SNR Hearing Protection Method: 
Single Number Rating method follows the ISO 4869-2:1995 standard.

SNR Calculator Details: 
To calculate the level of exposure at the ear, first enter the SNR number as listed on the hearing protective devices box or paper work that came with the device. Next measure the worker's Noise Exposure Level in dB(C). Enter tha measurement into the calculator and the result will be shown in the calculator. For real world calculation select +4dB

Calculation:
Result = NL - SNR
Real World (+4dB), Result = (NL - SNR) + 4dB

Definitions:
NL is the Noise Level or Sound Level measured in dB(C)
SNR is the Single Number Rating provided by the hearing protection device manufacturer

HML Method Details

The HML hearing protection method that takes into account the spectral characteristics of the offending noise when measuring the equivalent continuous ‘A’ (dB(A)) and ‘C’ (dB(C)) noise levels. The H, M, and L specifies attenuation values in (dB) at High, Medium, and Low frequencies, which are typically listed in the product documentation or packaging of the hearing protection device. 

HML Hearing Protection Method
The HML method follows the ISO standard method.

HML Calculator Details
To calculate the level of exposure at the ear, first enter the H, M and L number as listed on the hearing protective devices box or documentation that came with the device. Next measure the worker's Noise Exposure Level in dB(A) and dB(C). Enter these measured values in the calculator.

Step 1 

If	Calculation
dB(C)-dB(A)>=2dB	Result1 = M-(M-L)/8*(dB(C)-dB(A)-2)
dB(C)-dB(A)<=2dB	Result1 = M-(H-M)/4*(dB(C)-dB(A)-2)

Step 2
Result2 = dB(A) - Result1

Step 3
if Real World (+4dB), Result = (NL - SNR) + 4dB
else Result = Result2

Definitions 
NL is the Noise Level or Sound Level measured in dB(A) or dB(C)
H, M, L are the attenuation values in (dB) at High, Medium and Low Frequencies provided by the hearing protection device manufacturer

Octave Band Method Details

Octave Band Method uses frequency ranges to calculate the sound or noise level at the ear when wearing hearing protection. It is the most accurate method, but is also the most time consuming and complicated method. 

Octave Band Hearing Protection Method
The basis of audio fractional octave bands is a frequency of 1000Hz. There are two ways approved by ISO and ANSI in which the frequencies may be defined.

Octave Band Calculator Details
To calculate the level of exposure at the ear, first enter the Octave Band Assumed Protection number as listed on the hearing protective devices box or paper work that came with the device. Next measure the worker's Noise Exposure Level with Octave Band Filters. 

The formula:
 

Definitions:
NL is the Noise Level or Sound Level measured in either dB(A) or dB(C)
F is the frequency weighting
APV is the Assumed Protection Value derived from the mean attenuation provided by the device manufacturer