As the site says, "This collection is administered and maintained by the Houston Audio Control Room, at the NASA Johnson Space Center. The purpose of this collection is to make available the historic audio record of the history of Human Spaceflight at NASA, in an easily accessible and open manner. The audio contained in this collection has been digitized from original reel-to-reel tapes of varying format. Many tapes are the originals, from over 50 years ago. The original file format used to digitize and archive these historic audio tapes is WAV, at 48kHz / 24 bit. This WAV file is posted here, in the collection. Derivative formats are provided by the Internet Archive."
Special thanks to John Stoll and the rest of the ACR team at JSC for putting in long hours (in addition to their regular projects) to make these priceless pieces of history available in the highest quality formats and at no cost to the public.
I love reading or listening to the less well known moments of well known missions. Everyone knows "Tranquility base here, the Eagle has landed", but not many people are familiar with "Buzz, this is Neal. The space toilet is full, think we'd better open the window."
Seriously, there was a lot of minutiae that the public was not aware of. This is a fantastic resource.