NASA Auditory Demonstration Laboratory releases TWA Calculator v2.0

December 31, 2012

The NASA Auditory Demonstration Laboratory has released TWA Calculator v2.0, a computational and visual tool for teaching noise exposure dose concepts in an occupational hearing conservation context. TWA Calculator enables the user to easily create daily noise exposure scenarios from a series of component exposure events. TWA Calculator demonstrates the relationship between sound level, duration, and partial dose for each component exposure as well as their effect on the total dose and 8-hour noise exposure quantities [OSHA/MSHA Time-Weighted Average (TWA) and NIOSH LAeq,8], using both OSHA/MSHA and NIOSH values for criterion and exchange rate. Real-time changes in input data and calculated parameters are displayed graphically and numerically.

The upgraded TWA Calculator enables the application to read user-developed input files in the form of exposure scenarios and calculation properties tabulated in spreadsheet format.   Similarly, an exposure/calculation scenario developed while using TWA Calculator may be saved in a spreadsheet format and later read as an input file.  This new capability allows instructors to easily prepare and save example cases ahead of time and facilitates the use of TWA Calculator as a self-study and homework tool.

We’re looking for some input from users:

  • Do you have any examples that you’d be willing to contribute to a collection that would be offered on the EARLAB website as downloadable input files?   These examples would consist of numerical data in spreadsheet format with a short accompanying narrative on its intended use (teaching notes).  For instance, an example might consist of one or more 8-hour (or other-length) scenarios, each comprising a series of exposure events (sound levels and associated durations) that illustrate a particular concept or teaching point.  Teaching points could cover the effects of criterion/exchange rate, sound level threshold or rounding schemes as well as the effects of level/duration combinations on total exposure/dose.  Please contact us and let us know if you have a favorite example or teaching case you can share.


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