Presbycusis
--Measurement
tRobinson Sutton's Equations:  These equations were derived by combining a number of studies and are adopted for the values in ISO-1999 Annex A
     
tSpoor's Equations:  Combined data from 8 different studies.  Spoor accounted and controlled for noise in the derivations of his equations.
          
tOSHA (Occupational Safety and Health Administration) has published correction values for aging.  These values will correct threshold frequencies of 1000 Hz to 6000 Hz.  Since no values are given for 500 Hz, this method can only be used with the NIOSH and Wisconsin equations.