Audio Maximum Capture [AUD-P1]

Record Type: Audio Recordings

Expected Use: Preservation Master

Product Name: Audio Maximum Capture [AUD-P1]

Product Purpose: The purpose of this product is to mitigate the risk of loss of information. This file is at an appropriate information capture level to substitute for the original record if the original record copy is no longer viable.

Nature of Source Material: Any analog recording where there is a need to ensure that all significant auditory information is carried forward.

Possible File Derivatives: This master file can be used to create any preservation, reproduction or distribution file of equal or lesser capture quality.

File Properties

Container Format
  • Broadcast WAV (.wav) as defined by The European Broadcasting Union in document Tech 3285
  • Uncompressed
  • Version: 1

Typical file size for Mono: ~ 17.28 MB/minute or 1 GB/hour

Typical file size for Stereo: ~ 34.56 MB/minute or 2 GB/hour

File Specifications
  • Encoded to Linear Pulse Code Modulation (LPCM)

  • Sampling frequency: 96 kHz

  • Bit depth: 24

  • Sound field: as in original recording

  • Byte order: Little endian

Quality Control

Quality Control for Preservation Master Audio Products: NARA uses a commercially available, automated batch processing software tool to evaluate specific quality metrics. Below is an outline of our current processes for WAV products.

Metadata: 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.

Embedded metadata compliance: NARA follows the FADGI Embedded Metadata in Broadcast WAVE File Guidelines.

Technical metadata: NARA uses BWF MetaEdit to embed basic technical metadata, including Coding History. 

Item Level Evaluation: Automated File Characteristics Analysis

Fixity: NARA creates a checksum on the local workstation where the file is created.  This checksum is verified once the file reaches long-term tape storage to ensure that no changes have occurred during QA/QC procedures and file transfers on networked storage. 

Item Level Evaluation: Automated Quality Analysis

Using automated batch processing software tools, test plans are developed for each format and/or each appropriate project. The test plan allows for some characteristics to be evaluated on an actionable basis (warning, fail or pass depending on the defined parameters). Others are logged for internal use but are not actionable as a warning, pass or fail. Aim points for these benchmarks are evaluated against NARA's product specifications as well as NARA-defined aim points which may change depending on specific project goals. The following represents the quality test plan technical characteristics for WAV products.

Terms used in the QC protocols are defined in the Glossary of Terms.

Check (Warning/Pass/Fail)
  • Sampling Frequency (Hz)
  • Audio Channels (Number)
  • Bits per sample (Number)
Logged Data
  • Duration
  • Average audio level
  • Peak levels


The digital preservation masters products produced by the Audio Video Preservation Lab are in line with published guidelines and best practices including the IASA TC-04: Guidelines for the Production and Preservation of Digital Audio Objects and ARSC Preservation of Archival Sound Recordings.

Reproduction masters are also BWF files but at the minimum CD Quality specification.