- Audio restoration
Audio restoration is a generalized term for the process of removing imperfections (such as hiss, crackle,
noise, and buzz) from sound recordings. Audio restoration can be performed directly on the recording medium (for example, washing a gramophone recordwith a cleansing solution), or on a digitalrepresentation of the recording using a computer(such as a AIFFor WAVfile). Record restorationis a particular form of audio restoration that seeks to repair the sound of damaged records.
Modern audio restoration techniques are usually performed by
digitizingan audio source from analog media, such as lacquer recordings, optical sources and magnetic tape. Once in the digital realm, recordings can be restored and cleaned up using digital audio workstations (DAWs). DAWs can perform various automated techniques to remove anomalies using algorithms to accomplish broadband de-noising, de-crackle and de-hiss tasks. Often audio engineers and sound editors use DAWs to manually remove "pops and ticks" from recordings. DAWs are capable of removing the smallest of anomalies without leaving artifacts and other evidence of their removal. Audio restoration is often a time consuming process that requires skilled audio engineers with specific experience in music and film recording techniques.
The majority of audio restoration done today is done for music sound recordings and
soundtracks for motion picture and television programs. The demand for restored audio has been fueled by new media consumer technologies such as CDand DVD. Modern audio reproduction systems require that sound sources be in the best condition possible to enhance the listening experience. Media content owners have come to recognize the importance of having clean sound on their products to enhance the commercial value of their media assets.
The byproduct of these restoration efforts is that many audio sources are brought into the digital world and preserved for future use. An unfortunate fact is that most of the sound recordings and motion picture soundtracks created over the past century have been lost due to improper storage and neglect.
Enhancements are often done to motion picture soundtracks. For example taking a mono or stereo soundtrack and re-mixing it to a modern 5.1 surround soundtrack. When sources from original discrete audio "stems" containing dialog, music and sound effects are used and properly restored, the enhancements can be significant and highly effective.
Two researchers at
Lawrence Berkeley National Laboratory, Drs. Vitaliy Fadeyevand Carl Haber have been experimenting with an audio restoration method which involves taking a very high definition digital photographic image of the vintage recording medium. They use a precision optical metrologysystem (designed to scan silicon detectors) to form an image of the groove on a 78 rpmrecord. After processing the digital file, they have an audio stream that represents the variations in the groove walls, allowing them to 'play' the record virtually without using a phonograph stylus. 2D images can be made more quickly and have proved worthy of further investigation on 78 rpm discs cut laterally. A 3D method is possible, though it takes much longer for the photographic survey of the recording and it requires much more storage space for the larger digital file. 3D methods are required for non-flat media such as "hill-and-dale" recordings (an early vertical cutting method by Pathé), Edison cylinders and Dictabeltrolls. 3D imaging is required for stereo phonograph records in order to capture the full detail of both inner and outer groove walls. [ [http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/07/12/MNGJP7JRC21.DTL Digitizing the voices of the past / Science perfects sound of century-old recordings ] ] [ [http://sciencereview.berkeley.edu/articles.php?issue=7&article=briefs_5 The Berkeley Science Review: Read: Articles ] ] [ [http://www.lbl.gov/Science-Articles/Archive/Phys-quarks-to-blues.html Research News : From Top Quarks to the Blues ] ] [ [http://www.music.mcgill.ca/~ich/research/DDMAL/audio/ Audio preservation analogue recordings ] ]
In the summer of 2007, the U.S.
Library of Congressmoved their audio, video and film restoration group to Culpeper, Virginiawhere the newly completed National Audio-Visual Conservation CenterPackard Campus is sited. [ [http://www.loc.gov/avconservation/ A/V Conservation (Library of Congress) ] ] [ [http://www.loc.gov/avconservation/packard/ The Packard Campus - A/V Conservation (Library of Congress) ] ] Gene DeAnna heads the Recorded Sound Section. With 3 million sound recordings and many more film and video works that include synchronized sound in the archive, the mission of the Sound Section is twofold: preserve the treasure of vintage sound recordings and increase public accessibility to the collection. [ [http://www.loc.gov/avconservation/packard/mission.html Mission - The Packard Campus - A/V Conservation (Library of Congress) ] ] One of the ways that access can be increased is through the diligent digitization of analog media. The Library has expressed interest in the Fadeyev/Haber 2D imaging method for quick digital archival of their vast collection of vinyl and shellac phonograph records. Audio restoration tasks will take place in parallel with the digitization effort. A massive multipetabyte storage array is nearing completion; it will hold the large digital audio and moving image files. [ [http://www.gcn.com/print/26_17/44660-1.html Library of Congress redeploys ex-Federal Reserve bank vault as a high-capacity digital archive ] ]
Audio restoration is a subjective process, and there are many strategies or perspectives that the audio engineer or sound editor can employ. The archival perspective says that audio restoration should restore the recording to its original condition, while the commercial perspective says that the recording should be both restored and enhanced to appeal most immediately with modern audiences.
* [http://homerecording.about.com/od/recordingsoftwarereviews/Recording_Software_Reviews.htm?terms=Audio+restoration Review of several products on About.com]
* [http://www.audio-restoration.com/what-is.php What is Audio Restoration?] ( note: commercial site)
* [http://www.seewhyaudio.com/audio_restoration.htm What Is Digital Audio Restoration?] ( note: commercial site)
* [http://search.archives.gov/query.html?qt=audio+restoration Search the National Archive for "Audio Restoration"] (U.S. government website)
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