The NASA Auditory Demonstration Laboratory has produced TWA Calculator, 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.
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 replaces an earlier spreadsheet-based version of the calculator by the same name and was developed for the NASA Auditory Demonstration Laboratory by Nelson Acoustics 
.
TWA Calculator is available as a free downloadable application.