I read on the courts website that all post-1955 cases have recorded audio, it's available to the public, and it's maintained at the National Archive. All the stuff from 2010 to now is on the court's site as well as Oyez, but I cannot seem to find the rest. I wrote to the National Archive, but heard nothing back yet.
Do any of you know of an online archive of these audio files? Thank you so much!
Audio files of oral arguments for the period 1955-2012 are in the custody of the Motion Picture, Sound, and Video unit at Archives II in College Park, MD. Here is the description in the Catalog: https://catalog.archives.gov/id/105447
For more information about how to request copies, please contact that unit at firstname.lastname@example.org.