Source separation
Encyclopedia
Source separation problems in digital signal processing
are those in which several signals have been mixed together and the objective is to find out what the original signals were. The classical example is the "cocktail party problem", where a number of people are talking simultaneously in a room (like at a cocktail party
), and one is trying to follow one of the discussions. The human brain can handle this sort of auditory source separation problem, but it is a very tricky problem in digital signal processing. This was first analyzed by Colin Cherry
.
Several approaches have been proposed for the solution of this problem but development is currently still very much in progress. Some of the more successful approaches are principal components analysis
and independent components analysis, which work well when there are no delays or echoes present; that is, the problem is simplified a great deal. The field of computational auditory scene analysis
attempts to achieve auditory source separation using an approach that is based on human hearing.
The human brain must also solve this problem in real time. In human perception this ability is commonly referred to as auditory scene analysis
or the cocktail party effect
.
(MEG). This kind of imaging involves careful measurements of magnetic fields outside the head which yield an accurate 3D-picture of the interior of the head. However, external sources of electromagnetic fields, such as a wristwatch on the subject's arm, will significantly degrade the accuracy of the measurement. Applying source separation techniques on the measured signals can help remove undesired artifacts from the signal.
Another application is the separation of music
al signals. For a stereo mix of relatively simple signals it is now possible to make a pretty accurate separation, although some artifacts
remain.
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
are those in which several signals have been mixed together and the objective is to find out what the original signals were. The classical example is the "cocktail party problem", where a number of people are talking simultaneously in a room (like at a cocktail party
Cocktail party
A cocktail party is a party where cocktails are served. Women may choose to wear what has become known as a cocktail dress.Although many believe the inventor of the cocktail party to be Alec Waugh of London, who in 1924 found a need for this pleasant interlude before a dinner party, an article in...
), and one is trying to follow one of the discussions. The human brain can handle this sort of auditory source separation problem, but it is a very tricky problem in digital signal processing. This was first analyzed by Colin Cherry
Colin Cherry
Edward Colin Cherry was a British cognitive scientist whose main contributions were in focused auditory attention, specifically regarding the cocktail party problem. This concerns the problem of following only one conversation while many other conversations are going on around us...
.
Several approaches have been proposed for the solution of this problem but development is currently still very much in progress. Some of the more successful approaches are principal components analysis
Principal components analysis
Principal component analysis is a mathematical procedure that uses an orthogonal transformation to convert a set of observations of possibly correlated variables into a set of values of uncorrelated variables called principal components. The number of principal components is less than or equal to...
and independent components analysis, which work well when there are no delays or echoes present; that is, the problem is simplified a great deal. The field of computational auditory scene analysis
Computational auditory scene analysis
Computational auditory scene analysis is the study of auditory scene analysis by computational means . In essence, CASA systems are "machine listening" systems that aim to separate mixtures of sound sources in the same way that human listeners do...
attempts to achieve auditory source separation using an approach that is based on human hearing.
The human brain must also solve this problem in real time. In human perception this ability is commonly referred to as auditory scene analysis
Auditory scene analysis
In psychophysics, auditory scene analysis is the process by which the human auditory system organizes sound into perceptually meaningful elements. The term was coined by psychologist Albert Bregman...
or the cocktail party effect
Cocktail party effect
The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. The effect enables most people to talk in a noisy place...
.
Applications
One of the practical applications being researched in this area is medical imaging of the brain with magnetoencephalographyMagnetoencephalography
Magnetoencephalography is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs...
(MEG). This kind of imaging involves careful measurements of magnetic fields outside the head which yield an accurate 3D-picture of the interior of the head. However, external sources of electromagnetic fields, such as a wristwatch on the subject's arm, will significantly degrade the accuracy of the measurement. Applying source separation techniques on the measured signals can help remove undesired artifacts from the signal.
Another application is the separation of music
Music
Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...
al signals. For a stereo mix of relatively simple signals it is now possible to make a pretty accurate separation, although some artifacts
Sonic artifact
In sound and music production, sonic artifact, or simply artifact, refers to sonic material that is accidental or unwanted, resulting from the editing or manipulation of a sound....
remain.
See also
- Factorial codeFactorial codeMost real world data sets consist of data vectors whose individual components are not statistically independent, that is, they are redundant in the statistical sense. Then it is desirable to create a factorial code of the data, i...
s - Blind signal separationBlind signal separationBlind signal separation, also known as blind source separation, is the separation of a set of signals from a set of mixed signals, without the aid of information about the source signals or the mixing process....
- Independent component analysisIndependent component analysisIndependent component analysis is a computational method for separating a multivariate signal into additive subcomponents supposing the mutual statistical independence of the non-Gaussian source signals...
- Segmentation (image processing)Segmentation (image processing)In computer vision, segmentation refers to the process of partitioning a digital image into multiple segments . The goal of segmentation is to simplify and/or change the representation of an image into something that is more meaningful and easier to analyze...
- Speech segmentationSpeech segmentationSpeech segmentation is the process of identifying the boundaries between words, syllables, or phonemes in spoken natural languages. The term applies both to the mental processes used by humans, and to artificial processes of natural language processing....