University of Minnesota Digital Conservancy >

Digital Audio Guidelines

Introduction

The University Digital Conservancy encourages all those interested in preserving digital audio, either through direct digital capture or analog to digital conversion, to review the following recommendations. By doing so, Departments, faculty and staff are ensuring that the recording captured today will be of sufficient quality for current and future use and long-term preservation. All recommendations set forth by the University Digital Conservancy are based on current digital audio guidelines being developed and implemented at other organizations and universities.

Sample Rate & Bit Depth

The sample rate refers to the number of times per second the sound wave is measured, while the bit depth refers to the size or quality of said measurement. Both elements are crucial to capturing high quality digital audio. The following are guidelines to consider when capturing or converting your audio materials. When in doubt, it is best to chose a sampling rate and bit depth of sufficient quality, balancing your decision against the quality of the original recording.

Source Types

Knowing the source type of the analog recording can also help inform decisions as to which sample rate to choose when capturing these recordings digitally.

Spoken word recordings—the recommended sampling rate for spoken word recordings is 44.1 kHz.

Musical recordings—since these recordings can often carry the widest range of frequencies, we recommend a sampling rate of 96 kHz.

Combination recordings—for those recordings that involve a combination of spoken word, music, and/or natural sounds we recommend a sampling rate of 96 kHz.

File Formats

All audio files should be saved in file formats that best ensure the stability and long-term preservation of the files. To that end, the University Digital Conservancy recommends the use of non-proprietary and uncompressed formats whenever possible.

            Recommended file formats

WAV (.wav)             This file format was developed by Microsoft and is in widespread use and readable by a number of software applications.

AIF (.aif)             Developed by Apple Computer, this file format is also well supported and in widespread use.

The University Digital Conservancy will also accept other file formats, particularly MP3, though these may receive a lower level of service in preservation support.

References

“Best Practices for Producing High Quality Audio Files: Version 1.0”
Bentley Historical Library, University of Michigan
http://deepblue.lib.umich.edu/bitstream/2027.42/40248/1/Audio-Best_Practice.pdf

“Digital Audio Best Practices: Version 2.0”
Western States Digital Standards Group
Collaborative Digitization Program
http://www.cdpheritage.org/digital/audio/documents/CDPDABP_1-2.pdf

Go to the UDC home page