TWA Calculator is 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.
In an educational setting, a computer using TWA Calculator (when used with a computer projector system or at least the computer’s monitor) can display these concepts to large groups in a classroom environment and may also be used by students as a self-study aid for independent learning and practice.
TWA Calculator may also be used in a hearing conservation program management context to evaluate employee total daily noise exposure dose and TWA from monitoring data and make decisions regarding the need for program enrollment and personal hearing protector use as well as the implementation of administrative and engineered controls. TWA Calculator may be used as a desk-top calculator and graphic display to illustrate employee-specific noise exposure scenarios in a patient counseling environment.
TWA Calculator was developed using National Instruments LabVIEW™ v8.2.1 and requires a corresponding LabVIEW™ Run-time Engine to be present on the User’s computer. (Download the Run-time Engine for free. 
) A PC running Windows® 2000, Windows® XP or Windows Vista® is required. Windows® 7 has not yet been tested. Mac OS X is not supported.
TWA Calculator was produced by the NASA EARLAB Auditory Demonstration Laboratory, with application development contracted to Nelson Acoustics 
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- I will not redistribute TWA Calculator.
- I will not incorporate TWA Calculator in whole or part into any product, Web site, or other media that is redistributed or resold.
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TWA Calculator v2.0 (85 MB .zip file)
