In the mid-1990s, archivists at the Eisenhower Library discovered a collection of dictabelts of secretly recorded meetings from 1955. These tapes covered eight conversations with approximately 4 1/2 hours of recorded discussion. In 1997, in the papers of President Eisenhower's military aide, the Library found an even larger group of tapes, comprising an additional 10 hours of conversations from 1950-51 when General Eisenhower was considering a run for the Presidency. These tapes were made in General Eisenhower's offices at Columbia University, where he served as President, and, it is believed, at his office in Paris, where he served as Supreme NATO Commander.
The sound files can be downloaded in two formats: FLAC and MP3. Each has benefits for different uses.
MP3: good sound reproduction, smaller files, universally compatible. Very good for telephone or Dictabelt recordings and for general listening. If in doubt, try the MP3 versions first.
FLAC: excellent sound reproduction, larger files, growing compatibility. Recommended for meeting recordings and transcribing where the highest sound quality is required. In terms of sound quality, FLAC files are identical to WAV or AIFF files.
More detailed information is available here.