According to IASA TC-03 The Safeguarding of the Audio Heritage: Ethics, Principles and Preservation Strategy, preservation transfer should produce master files that are unmodified, "without subjective alterations or improvements."
Creating and storing an unaltered, unmodified digital file means no editing of content. Every second on the source recording, no matter how irrelevant, is transferred in order to obtain a full, authentic representation of the original recording. This preserves content that future researchers may find important in ways that we cannot anticipate today. In addition, the original sound field, whether stereo or mono, is preserved in the master archival file.
Berea’s master archival sound files are 24-bit, 96 kHz PCM encoded BWAV files, more than twice the resolution of standard CD audio. This ensures that the full range of reproduced material is captured and preserved with utmost accuracy.
Derivative audio files are created for any form of editing, signal processing, or other alterations from the original preservation file. This includes making reference CDs for in-house listening, and encoding MP3 files for online access through the Sound Archives Guide.