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Noise Calculators & Reporters - Newsletter - May 2009

A new Applications section on our web site offers the following calculators:

  • Occupational Noise
    • Time Weighted Average Calculator
    • Hearing Protection Calculator
  • Environmental Noise
    • Ldn, Lden, CNEL Calculator
  • General Purpose
    • Decibel Calculator

The Occupational Noise calculators ease your task by providing printed reports. Online context-sensitive help will guide you through the process.

Link: Noise Applications and Calculators

decibel and noise calculators


Andrew Snell

TWA Calculator and Report Maker
The magical Time Weighted Average

To calculate a worker's TWA you take the sound level and time spent at each location, do a few logs and anti-logs, apply some magic and get the TWA.

If you are all out of magic, you might find our TWA calculator useful. Enter the locations, levels and times, and it does the rest, even printing a report for your records.

Link: TWA Calculator

twa and noise dose calculator

Hearing Protection Calculator
Do you know the level of protection?

You may calculate the sound level at the worker's ear when wearing hearing protection using either the popular NRR method or the more detailed HML and Octave Band calculations.

The easiest method, taking a protector's Noise Reduction Rating figure and applying it to the measured noise. The calculator can follow either the OSHA or NIOSH guidelines.

Link: NRR Hearing Protection Calculator

Slightly more detailed, requiring both "A" and "C" weighted measurements and the protector's H-M-L figures.

Link: HML Hearing Protector Calculator

nrr hearing protection calculator

Octave Band
The most detailed method, requiring Octave Band measurements and the APV figures for the hearing protector.

Link: Octave Band Protector Calculator

octave band hearing protector calculations

Ldn and Lden (CNEL) Calculator
Calculated from the 1-hour Leq

Ldn and Lden (or CNEL) is often used when checking the impact of noise on a community from a source such as an airport or road.

As people are more sensitive to noise at night, Ldn adds a 10dB weighting to levels between 10pm and 7am. The Lden and CNEL measurements go one step further and add 5dB to levels between 7pm and 10pm.

Our calculator can take hourly Leq measurements and calculate the Ldn and Lden for the full 24 hour period.

Link: Ldn and Lden Calculator

ldn lden and cnel calculator

Decibel Calculator
1 + 1 = 4

A useful tool for a lesson in dB math. As they are logarithmic, decibels cannot just be added together:

log sum for decibels

Or use the calculator: dB Calculator

decibel calculator

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