Audio restoration
Encyclopedia
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 record
with a cleansing solution), or on a digital
representation of the recording using a computer
(such as a AIFF
or WAV
file). Record restoration
is a particular form of audio restoration that seeks to repair the sound of damaged records.
Modern audio restoration techniques are usually performed by digitizing
an 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 dedicated, standalone digital processing units such as declickers, decracklers, dehissers and dialogue noise suppressors, or using digital audio workstations (DAWs)
. DAWs can perform various automated techniques to remove anomalies using algorithms to accomplish broadband denoising, declicking and decrackling, as well as removing buzzes and hums. Often audio engineer
s and sound editors use DAWs to manually remove "pops and ticks" from recordings, and the latest spectrographic 'retouching' techniques allow for the suppression or removal of discrete unwanted sounds. DAWs are capable of removing the smallest of anomalies, often without leaving artifacts and other evidence of their removal. Although fully automated solutions exist, audio restoration is sometimes a time consuming process that requires skilled audio engineers with specific experience in music and film recording techniques.
s for motion picture
and television program
s. The demand for restored audio has been fueled by new media consumer technologies such as CD and 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.
, Drs. Vitaliy Fadeyev and 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 metrology system (designed to scan silicon detectors) to form an image of the groove on a 78 rpm record. 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 Dictabelt
rolls. 3D imaging is required for stereo phonograph records in order to capture the full detail of both inner and outer groove walls.
In the summer of 2007, the U.S. Library of Congress
moved their audio, video and film restoration group to Culpeper, Virginia
where the newly completed National Audio-Visual Conservation Center Packard Campus is sited. 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. 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.
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.
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...
, crackle, noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
, and buzz) from sound recordings
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
. Audio restoration can be performed directly on the recording medium (for example, washing a gramophone record
Gramophone record
A gramophone record, commonly known as a phonograph record , vinyl record , or colloquially, a record, is an analog sound storage medium consisting of a flat disc with an inscribed, modulated spiral groove...
with a cleansing solution), or on a digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
representation of the recording using a computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
(such as a AIFF
AIFF
Audio Interchange File Format is an audio file format standard used for storing sound data for personal computers and other electronic audio devices...
or WAV
WAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...
file). Record restoration
Record restoration
Record restoration, a particular kind of audio restoration, is the process of converting theanalog signal stored on gramophone records Record restoration, a particular kind of audio restoration, is the process of converting theanalog signal stored on gramophone records Record restoration, a...
is a particular form of audio restoration that seeks to repair the sound of damaged records.
Modern audio restoration techniques are usually performed by digitizing
Digitizing
Digitizing or digitization is the representation of an object, image, sound, document or a signal by a discrete set of its points or samples. The result is called digital representation or, more specifically, a digital image, for the object, and digital form, for the signal...
an audio source from analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
media, such as lacquer recordings, optical sources
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...
and magnetic tape. Once in the digital realm, recordings can be restored and cleaned up using dedicated, standalone digital processing units such as declickers, decracklers, dehissers and dialogue noise suppressors, or using digital audio workstations (DAWs)
Digital audio workstation
A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...
. DAWs can perform various automated techniques to remove anomalies using algorithms to accomplish broadband denoising, declicking and decrackling, as well as removing buzzes and hums. Often audio engineer
Audio engineering
An audio engineer, also called audio technician, audio technologist or sound technician, is a specialist in a skilled trade that deals with the use of machinery and equipment for the recording, mixing and reproduction of sounds. The field draws on many artistic and vocational areas, including...
s and sound editors use DAWs to manually remove "pops and ticks" from recordings, and the latest spectrographic 'retouching' techniques allow for the suppression or removal of discrete unwanted sounds. DAWs are capable of removing the smallest of anomalies, often without leaving artifacts and other evidence of their removal. Although fully automated solutions exist, audio restoration is sometimes a time consuming process that requires skilled audio engineers with specific experience in music and film recording techniques.
Overview
The majority of audio restoration done today is done for music sound recordings and soundtrackSoundtrack
A soundtrack can be recorded music accompanying and synchronized to the images of a motion picture, book, television program or video game; a commercially released soundtrack album of music as featured in the soundtrack of a film or TV show; or the physical area of a film that contains the...
s for motion picture
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
and television program
Television program
A television program , also called television show, is a segment of content which is intended to be broadcast on television. It may be a one-time production or part of a periodically recurring series...
s. The demand for restored audio has been fueled by new media consumer technologies such as CD and DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
. 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
Monaural
Monaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
or stereo
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
soundtrack and re-mixing
Audio mixing (recorded music)
In audio recording, audio mixing is the process by which multiple recorded sounds are combined into one or more channels, most commonly two-channel stereo. In the process, the source signals' level, frequency content, dynamics, and panoramic position are manipulated and effects such as reverb may...
it to a modern 5.1 surround soundtrack
Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
. 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.
Recent developments
Two researchers at Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory , is a U.S. Department of Energy national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus...
, Drs. Vitaliy Fadeyev and 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 metrology system (designed to scan silicon detectors) to form an image of the groove on a 78 rpm record. 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 Dictabelt
Dictabelt
The Dictabelt or Memobelt was a form of recording medium introduced by the American Dictaphone company in 1947. It used a type of "Write Once - Read Many" medium consisting of a thin, plastic belt 3.5" wide that was placed on a cylinder and spun like a tank tread. The needle would then move slowly...
rolls. 3D imaging is required for stereo phonograph records in order to capture the full detail of both inner and outer groove walls.
In the summer of 2007, the U.S. Library of Congress
Library of Congress
The Library of Congress is the research library of the United States Congress, de facto national library of the United States, and the oldest federal cultural institution in the United States. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and...
moved their audio, video and film restoration group to Culpeper, Virginia
Culpeper, Virginia
Culpeper is an incorporated town in Culpeper County, Virginia, United States. The population was 9,664 at the 2000 census. It is the county seat of Culpeper County. Culpeper is part of the Culpeper Micropolitan Statistical Area, which includes all of Culpeper County. Both the Town of Culpeper and...
where the newly completed National Audio-Visual Conservation Center Packard Campus is sited. 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. 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.
Subjective issues
Audio restoration is a subjectiveSubjectivity
Subjectivity refers to the subject and his or her perspective, feelings, beliefs, and desires. In philosophy, the term is usually contrasted with objectivity.-Qualia:...
process, and there are many strategies or perspectives that the audio engineer or sound editor can employ. The archival
Archive
An archive is a collection of historical records, or the physical place they are located. Archives contain primary source documents that have accumulated over the course of an individual or organization's lifetime, and are kept to show the function of an organization...
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.
External links
- Manual of analogue audio restoration techniques (The British Library Sound Archive)