Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids: - A Novel Approach to Unbiased Feedback Cancellation

Meng Guo

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

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Resumé

Acoustic feedback problems occur when the output loudspeaker signal of an audio system
is partly returned to the input microphone via an acoustic coupling through the air. This
problem often causes significant performance degradations in applications such as public
address systems and hearing aids. In the worst case, the audio system becomes unstable
and howling occurs.
In this work, first we analyze a general multiple microphone audio processing system,
where a cancellation system using adaptive filters is used to cancel the effect of
acoustic feedback. We introduce and derive an accurate approximation of a frequency
domain measure—the power transfer function—and show how it can be used to predict
the convergence rate, system stability bound, and the steady-state behavior of the entire
cancellation system across time and frequency without knowing the true acoustic
feedback paths. This power transfer function method is also applicable to an acoustic
echo cancellation system with a similar structure.
Furthermore, we consider the biased estimation problem, which is one of the most
challenging problems for state-of-the-art acoustic feedback cancellation systems. A commonly
known approach to deal with the biased estimation problem is adding a probe
noise signal to the loudspeaker signal and base the estimation on that. This approach
is particularly promising, since it can be shown that, in theory, the biased estimation
problem can be completely eliminated. However, we analyze a traditional probe noise
approach and conclude that it can not work in most acoustic feedback cancellation
systems in practice, due to the very low convergence rate of the adaptive cancellation
system when using low level and inaudible probe noise signals.
We propose a novel probe noise approach to solve the biased estimation problem in
acoustic feedback cancellation for hearing aids. It utilizes a probe noise signal which
is generated with a specific characteristic so that it can facilitate an unbiased adaptive
filter estimation with fast tracking of feedback path variations/changes despite its low
signal level. We show in a hearing aid application that whereas the traditional and stateof-
the-art acoustic feedback cancellation systems fail with significant sound distortions
and howling as consequences, the new probe noise approach is able to remove feedback
artifacts caused by the feedback path change in no more than a few hundred milliseconds.
OriginalsprogEngelsk
Antal sider224
ISBN (Trykt)978-87-7152-001-9
StatusUdgivet - 2013

Fingeraftryk

Hearing aids
Acoustics
Feedback
Loudspeakers
Microphones
Audio systems
Adaptive filters
System stability
Transfer functions
Acoustic waves
Degradation

Citer dette

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title = "Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids: - A Novel Approach to Unbiased Feedback Cancellation",
abstract = "Acoustic feedback problems occur when the output loudspeaker signal of an audio systemis partly returned to the input microphone via an acoustic coupling through the air. Thisproblem often causes significant performance degradations in applications such as publicaddress systems and hearing aids. In the worst case, the audio system becomes unstableand howling occurs.In this work, first we analyze a general multiple microphone audio processing system,where a cancellation system using adaptive filters is used to cancel the effect ofacoustic feedback. We introduce and derive an accurate approximation of a frequencydomain measure—the power transfer function—and show how it can be used to predictthe convergence rate, system stability bound, and the steady-state behavior of the entirecancellation system across time and frequency without knowing the true acousticfeedback paths. This power transfer function method is also applicable to an acousticecho cancellation system with a similar structure.Furthermore, we consider the biased estimation problem, which is one of the mostchallenging problems for state-of-the-art acoustic feedback cancellation systems. A commonlyknown approach to deal with the biased estimation problem is adding a probenoise signal to the loudspeaker signal and base the estimation on that. This approachis particularly promising, since it can be shown that, in theory, the biased estimationproblem can be completely eliminated. However, we analyze a traditional probe noiseapproach and conclude that it can not work in most acoustic feedback cancellationsystems in practice, due to the very low convergence rate of the adaptive cancellationsystem when using low level and inaudible probe noise signals.We propose a novel probe noise approach to solve the biased estimation problem inacoustic feedback cancellation for hearing aids. It utilizes a probe noise signal whichis generated with a specific characteristic so that it can facilitate an unbiased adaptivefilter estimation with fast tracking of feedback path variations/changes despite its lowsignal level. We show in a hearing aid application that whereas the traditional and stateof-the-art acoustic feedback cancellation systems fail with significant sound distortionsand howling as consequences, the new probe noise approach is able to remove feedbackartifacts caused by the feedback path change in no more than a few hundred milliseconds.",
author = "Meng Guo",
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Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids : - A Novel Approach to Unbiased Feedback Cancellation. / Guo, Meng.

2013. 224 s.

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

TY - BOOK

T1 - Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids

T2 - - A Novel Approach to Unbiased Feedback Cancellation

AU - Guo, Meng

PY - 2013

Y1 - 2013

N2 - Acoustic feedback problems occur when the output loudspeaker signal of an audio systemis partly returned to the input microphone via an acoustic coupling through the air. Thisproblem often causes significant performance degradations in applications such as publicaddress systems and hearing aids. In the worst case, the audio system becomes unstableand howling occurs.In this work, first we analyze a general multiple microphone audio processing system,where a cancellation system using adaptive filters is used to cancel the effect ofacoustic feedback. We introduce and derive an accurate approximation of a frequencydomain measure—the power transfer function—and show how it can be used to predictthe convergence rate, system stability bound, and the steady-state behavior of the entirecancellation system across time and frequency without knowing the true acousticfeedback paths. This power transfer function method is also applicable to an acousticecho cancellation system with a similar structure.Furthermore, we consider the biased estimation problem, which is one of the mostchallenging problems for state-of-the-art acoustic feedback cancellation systems. A commonlyknown approach to deal with the biased estimation problem is adding a probenoise signal to the loudspeaker signal and base the estimation on that. This approachis particularly promising, since it can be shown that, in theory, the biased estimationproblem can be completely eliminated. However, we analyze a traditional probe noiseapproach and conclude that it can not work in most acoustic feedback cancellationsystems in practice, due to the very low convergence rate of the adaptive cancellationsystem when using low level and inaudible probe noise signals.We propose a novel probe noise approach to solve the biased estimation problem inacoustic feedback cancellation for hearing aids. It utilizes a probe noise signal whichis generated with a specific characteristic so that it can facilitate an unbiased adaptivefilter estimation with fast tracking of feedback path variations/changes despite its lowsignal level. We show in a hearing aid application that whereas the traditional and stateof-the-art acoustic feedback cancellation systems fail with significant sound distortionsand howling as consequences, the new probe noise approach is able to remove feedbackartifacts caused by the feedback path change in no more than a few hundred milliseconds.

AB - Acoustic feedback problems occur when the output loudspeaker signal of an audio systemis partly returned to the input microphone via an acoustic coupling through the air. Thisproblem often causes significant performance degradations in applications such as publicaddress systems and hearing aids. In the worst case, the audio system becomes unstableand howling occurs.In this work, first we analyze a general multiple microphone audio processing system,where a cancellation system using adaptive filters is used to cancel the effect ofacoustic feedback. We introduce and derive an accurate approximation of a frequencydomain measure—the power transfer function—and show how it can be used to predictthe convergence rate, system stability bound, and the steady-state behavior of the entirecancellation system across time and frequency without knowing the true acousticfeedback paths. This power transfer function method is also applicable to an acousticecho cancellation system with a similar structure.Furthermore, we consider the biased estimation problem, which is one of the mostchallenging problems for state-of-the-art acoustic feedback cancellation systems. A commonlyknown approach to deal with the biased estimation problem is adding a probenoise signal to the loudspeaker signal and base the estimation on that. This approachis particularly promising, since it can be shown that, in theory, the biased estimationproblem can be completely eliminated. However, we analyze a traditional probe noiseapproach and conclude that it can not work in most acoustic feedback cancellationsystems in practice, due to the very low convergence rate of the adaptive cancellationsystem when using low level and inaudible probe noise signals.We propose a novel probe noise approach to solve the biased estimation problem inacoustic feedback cancellation for hearing aids. It utilizes a probe noise signal whichis generated with a specific characteristic so that it can facilitate an unbiased adaptivefilter estimation with fast tracking of feedback path variations/changes despite its lowsignal level. We show in a hearing aid application that whereas the traditional and stateof-the-art acoustic feedback cancellation systems fail with significant sound distortionsand howling as consequences, the new probe noise approach is able to remove feedbackartifacts caused by the feedback path change in no more than a few hundred milliseconds.

M3 - Ph.D. thesis

SN - 978-87-7152-001-9

BT - Analysis, Design, and Evaluation of Acoustic Feedback Cancellation Systems for Hearing Aids

ER -