Audio Recovery Project
written by Cynthia L. Cochran, May 1, 2006
The ARP was first proposed in 1996
Four reel to reel tape decks, playing back two channels each (left and right stereo), feed sound into the M-Audio 8 channel digital I/O card that converts the analog audio signal to digital using a sampling rate of 44.1.kHz (the number of times per second the amplitude of the wave is measured) and a bit depth of 24 (the range of numbers used to record each measurement). Steinberg’s Cubase SX software is used to capture and record the digital signals in WAV file format to an array of six 400 GB Seagate SATA hard drives in RAID 5 configuration on a dual processor Zeon Intel computer server with 2 GB of RAM. No signal filtering or processing is conducted on these master preservation digital files. The RAID 5 configuration provides an additional level of data security because each hard drive reserves part of its data space to record parity information that will allow all data to be recovered if a single drive ever fails. A second computer is used to create four additional copies of this master preservation file, two recorded to Mitsui Gold DVD-R discs, and two recorded to Mitsui Gold CD-R discs, dithered down to 16 bit
depth. These discs provide “back up in case the RAID computer dies suddenly, . . . [and one disc of each media is] stored off-site in case the archive building dies suddenly” (Levy, email to author, 27 April 2006).
A third computer utilizes Steinberg’s Wavelab two track audio editor software, with plug-ins from Waves, Inc., to restore and re-master the 24 bit master file. The audio technician “remove[s] low frequencies, such as hum and traffic noises, fans, air conditioners, etc.; remove[s] some hiss from the high frequencies; use[s] a broad band de-noiser for really noisy situations; boost[s] [the volume of] questions [from the audience], if the audience is not ‘miked’; [and] boost[s] and fatten[s] the overall signal using varying amounts of audio compression to bring up the volume in quieter parts to achieve a more linear dynamic range” (Levy, email to author, 27 April 2006). Two copies of the re-mastered, 24 bit, 44.1kHz file are recorded to Mitsui Gold DVD-R, one for off-site storage. A 16 bit, 44.1 kHz CD image file is created and copied, via Ethernet network, to the internal hard drive of a professional DVD/CD duplicator.
Finally, an MP3 file, encoded at 44.1 kHz and 128 kbs, is created from the re-mastered file and stored to the RAID hard drives on the server. An MP3 file that provides an audio demonstration of the quality improvements from the re-mastering process is available for download from the Archives web site at http://www.shambhalashop.com/archives by clicking on the link entitled “Audio Recovery Project.”
Dissemination and Access
Assessment and Conclusion
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