Hello,
With the most recent versions of PennController, the media files are named after the element’s name, so if you have newMediaRecorder( "production", "audio" ) then the filename will be production.webm (assuming your browser saves the audio file as webm, and you have no other MediaRecorder element named production in the course of your experiment).
The uploaded zip files containing the audio files, however, are named using (almost perfectly) unique strings, to avoid upload conflict issues, and also because the various audio files from the same trial or even from multiple trials can all end up packaged in a single zip file in a non-deterministic way
Jeremy