Digitization of Audio Files

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Introduction

When working with audio data, it is important to keep long-term intelligibility in mind. Many recording media, such as magnetic tapes, are prone to decay. Some storage formats may require frequent conversion due to the forced obsolescence of the application that was used to create them. Other formats entail lossy compression, which results in the loss of valuable sound data. This section of the School provides advice on audio data quality, storage and digitization.

Audio digitization quality issues

Unlike paper records, which have a long life-span, analog sound recording media are subject to deterioration within a few decades. Much of our information about endangered languages has been recorded on magnetic tapes, whether cassette or reel-to-reel, and these are far from permanent storage materials. Until recently, audio archivists handled this situation by periodically re-recording audio on fresh tapes. However, there is always a loss of quality when analog recordings are copied, while digital copies are identical in quality, providing an error checking routine is used to verify identity. Digitization provides a better method for preservation of audio recordings, but it is important to realize that this will also require periodic migration to new physical media (e.g., from CDs to DVDs, or from one server to another) and new software formats (e.g., from WAV to the next version).

More on quality issues

Audio formats

When working with audio data, two formats must be considered: an archival format and a presentation format. In general, the archival copy should not be cleaned up or enhanced in any way, since this entails a loss of some portion of the original data. Presentation copies may be processed whenever appropriate to make the sound more accessible, but the archival master should be a faithful representation of the original recording.

More on archival format
More on presentation format

How to digitize audio data

Some formats, such as wax cylinders, lacquer discs, and wire recordings, are too fragile to be digitized by the average linguist, and should be handled by professionals. However, many field linguists have magnetic tapes that are candidates for digitization, both to make them more accessible, and to preserve them before they deteriorate. Caution: If the tape shows signs of decay (e.g., mold, or any visible damage to the tape layers), consult an audio preservation specialist first; any attempt to play a damaged tape may ruin it. But if the tape appears to be in good shape, you should be able to convert it yourself.

Step by step digitization instructions
Equipment recommendations


The content of this page was developed following the recommendations from The NINCH Guide to Good Practice,  The Collaborative Digitization Program,  The Vincent Voice Library Digital Audio Specifications, and  Audio Digitization for Archival Purposes.

See also Sound Directions: Best Practices for Audio Preservation.

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Digitization of Audio Files
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