Audio Online Delivery MP3 [AUD-D2]

Record Type: Audio Recordings

Expected Use: Distribution Copy

Product Name: Audio Online Delivery MP3 [AUD-D2]

Product Purpose: This product is primarily used for online delivery through the National Archives Catalog.  Product is also served as a reference copy on site in National Archives and Records Administration (NARA) Moving Image and Sound Research Room.

Nature of Source Material: Any digital preservation or reproduction master file.

Possible File Derivatives: Derivatives are not made from this product category.

Other Information: Reproduction and distribution files may have additional improvements such as the application of an equalization (EQ) curve for grooved discs.

File Properties

Container Format
Capture Information

Typical file size for Mono: 128 Kbps: ~ .96 MB/minute or .057 GB/hour

Typical file size for Stereo: 256 Kbps: ~ 1.9 MB/ minute or .113 GB/hour

Quality Control

Quality Control for Distribution Copy Audio Files

The Audio–Video Lab relies on visual and auditory quality control (QC) and spot checks to confirm completeness and technical characteristics of the files.


MP3 files are tagged with local identifier information for access purposes - no additional information is embedded. The filename contains metadata that associates the file with external sources of descriptive and technical metadata. Each filename is a unique identifier composed of the item’s record group, series, and item number.


Reproduction masters are at a high enough quality that they may be used in a production context.  Distribution copies are at a low enough bitrate that they are able to be easily streamed or downloaded via an internet connection.