Dear Conrad -- thank you for posting to History Hub!
The published transcripts of congressional hearings can be found through ProQuest Congressional, a subscription database. Transcripts can also sometimes be found freely available online through sources like Hathi Trust, Google Books, and the Internet Archive.
Regarding audio and video, the responsibility for filming public hearings generally falls to C-SPAN and the news media. Copies of that footage rarely, if ever, end up in the official records of congressional committees.You can also check with film and television archival repositories such as UCLA's Film & Television Archive or Vanderbilt's Television News Archive.
For more background on audio and video recordings of the House and the Senate there's a Congressional Research Service report: Video Broadcasting of Congressional Proceedings (April 2017).