From Substrate to Streaming: Audio Archives at KBOO


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Authored by: 
Published date: 
Tuesday, December 6, 2016 - 6:15am

What goes into digitizing audio content? 

Some of KBOO's archival audio content sits on 1/4" audio tape. The majority of the tape's substrate is polyester base, with a few acetate base tapes. Both of these types of tape have their own challenges for preservation. Polyester base tape typically can present a "sticky-shed" syndrome that affects playback and quality of tape. It is reversible, but affects longevity of the tape. Acetate base tape can present "vinegar syndrome" which is a sign of substrate deterioration. Digital preservation is a method of preservation that requires its own care and handling of newly created materials. Files made of bits and bytes need to be managed to ensure that the file's bit and byte structure remains fixed and is playable with audio software.

Audiovisual digitization vendors provide a service with specific details. I developed an RFP (request for proposals) for vendors that is specific to the digital preservation needs of KBOO for 1/4" open reel audio items the archive collection. It was created using an RFP template from AV Preserve.

KBOO RFP for open reel digitization

An RFP, or a RFI (request for information) is a chance for an audiovisual archive to ensure that what it wants will be included in the service at a particular cost, and allows the organization to budget appropriately. You will notice that our RFP includes sections on care and handling, appropriate storage at the vendor facility, documentation of metadata, sample rate and bit depth of audio files created, and a request for no sound processing, among other details. Digital preservation differs from the creation of a produced sound file. KBOO wishes to preserve the best quality of analog audio content as it is represented on the tape. So, if the audio was originally recorded with background noise or varying  audio levels, these are kept in the preservation file. Often, keeping details in offer contextual information about how audio was created. For listening ease, lower quality mp3 files are created from the preservation wav file and an organization can determine how much editing it wishes to perform for these proxy or derivative files.

Sending reels out for specific and detailed work of digitization is only one step in KBOO's workflow for open reel audio digital preservation. In brief, the workflow is presented below (two images). You'll noticed that KBOO is continuously working on improving the information documented about audio items and managing it in an archive access system, and that it is a group effort! A collective wisdom of many KBOO volunteers is necessary to add more information to sparsely documented audio tapes.

At the end of the workflow, KBOO's radio content will have moved from the physical substrate of the tape to a streaming file format that is accessible to researchers and patrons.