The well known voice of Randy Goyer can be heard on MicroHBD & Micro Talker units all across North America. Little has changed with the audio of these units since their debut by GE Transportation Systems in the early 2000s, although the units have undergone many internal upgrades.
For the trained ear, you may be able to discern early GE Micro Talkers from more contemporary products. You can hear an ever so slight pauses between the word "track" and the track number, as well as between the letters in "CSX." Additionally, these units say "axles" while MicroHBD units say "axle" (singular). Unfortunately, newer Micro Talkers have no discernable difference in voice and can only be identified by their functionality as found in an employee timetable.
-Information courtesy of Nick Wilson from defectdetector.net
Here's a sample of what the detector's voice will sound like in the sim