Adaptive feedback cancellation
Encyclopedia
Adaptive feedback
cancellation is a common method of cancelling audio feedback
in a variety
of electro-acoustic systems such as digital hearing aid
s. The time varying acoustic feedback leakage paths can only be eliminated with adaptive feedback cancellation. When an electro-acoustic system with an adaptive feedback canceller is presented with a correlated input signal, a recurrent distortion
artifact, entrainment
is generated. There is a difference between the system identification and feedback cancellation.
Adaptive feedback cancellation has its application in echo cancellation
. The error between the desired and the actual output is taken and given as feedback to the adaptive processor for adjusting its coefficients to minimize the error.
http://www.hearingreview.com/graphics/mags/0604/f06a.jpg
In hearing aids, feedback arises when a part of the receiver (loudspeaker) signal is captured by the hearing aid microphone(s), gets amplified in the device and starts to loop around through the system. When feedback occurs, it results in a disturbingly loud tonal signal. Feedback is more likely to occur when the hearing aid volume is increased, when the hearing aid fitting is not in its proper position or when the hearing aid is brought close to a reflecting surface (e.g. when using a mobile phone). Adaptive feedback cancellation algorithms are techniques that estimate the transmission path between loudspeaker and microphone(s). This estimate is then used to implement a neutralizing electronic feedback path that suppresses the tonal feedback signal.
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
cancellation is a common method of cancelling audio feedback
Audio feedback
Audio feedback is a special kind of positive feedback which occurs when a sound loop exists between an audio input and an audio output...
in a variety
of electro-acoustic systems such as digital hearing aid
Hearing aid
A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...
s. The time varying acoustic feedback leakage paths can only be eliminated with adaptive feedback cancellation. When an electro-acoustic system with an adaptive feedback canceller is presented with a correlated input signal, a recurrent distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
artifact, entrainment
Entrainment (physics)
Entrainment has been used to refer to the process of mode locking of coupled driven oscillators, which is the process whereby two interacting oscillating systems, which have different periods when they function independently, assume a common period...
is generated. There is a difference between the system identification and feedback cancellation.
Adaptive feedback cancellation has its application in echo cancellation
Echo cancellation
'The term echo cancellation is used in telephony to describe the process of removing echo from a voice communication in order to improve voice quality on a telephone call...
. The error between the desired and the actual output is taken and given as feedback to the adaptive processor for adjusting its coefficients to minimize the error.
http://www.hearingreview.com/graphics/mags/0604/f06a.jpg
In hearing aids, feedback arises when a part of the receiver (loudspeaker) signal is captured by the hearing aid microphone(s), gets amplified in the device and starts to loop around through the system. When feedback occurs, it results in a disturbingly loud tonal signal. Feedback is more likely to occur when the hearing aid volume is increased, when the hearing aid fitting is not in its proper position or when the hearing aid is brought close to a reflecting surface (e.g. when using a mobile phone). Adaptive feedback cancellation algorithms are techniques that estimate the transmission path between loudspeaker and microphone(s). This estimate is then used to implement a neutralizing electronic feedback path that suppresses the tonal feedback signal.