3,971 research outputs found
New Insights into Optimal Acoustic Feedback Cancellation
In this letter, we present new insights into the bias problem for acoustic feedback cancellation when a probe signal approach is used. The optimum solution of the feedback canceler is not the feedback path but the product of the feedback path and the sensitivity function and hence, the solution is biased. The novelty of this paper also consists of the derivation of the conditions for unbiased feedback cancellation when a probe signal is used as input to the canceler. An adequate delay in the forward path is necessary to reduce, or remove the bias term. The theoretical analysis is verified with simulation results
Control of feedback for assistive listening devices
Acoustic feedback refers to the undesired acoustic coupling between the loudspeaker and microphone in hearing aids. This feedback channel poses limitations to the normal operation of hearing aids under varying acoustic scenarios. This work makes contributions to improve the performance of adaptive feedback cancellation techniques and speech quality in hearing aids. For this purpose a two microphone approach is proposed and analysed; and probe signal injection methods are also investigated and improved upon
Feedback cancellation with probe shaping compensation
Adaptive feedback cancellation methods may integrate the use of probe signals to assist with the biased optimal solution in acoustic systems working in closed-loop. However, injecting a probe noise in the loudspeaker decreases the signal quality perceived by users of assistive listening devices. To counter this, probe signals are usually shaped to provide some level of perceptual masking. In this letter we show the impact of using a shaping filter on the system behavior in terms of convergence rate and steady state error. From this study, it can be concluded that shaping the probe signal may have detrimental influence in terms of system performance. Accordingly, we propose to use the unshaped probe signal combined with an inverse filter of the shaping filter to identify the feedback channel. This restructure of the problem restores convergence rate of LMS type algorithms. Furthermore, we also show that an adequate forward path delay is required to obtain an unbiased solution and that the suggested scheme reduces this delay
Digital Signal Processing Research Program
Contains table of contents for Section 2, an introduction, reports on twenty-two research projects and a list of publications.Sanders, a Lockheed-Martin Corporation Contract BZ4962U.S. Army Research Laboratory Contract DAAL01-96-2-0001U.S. Navy - Office of Naval Research Grant N00014-93-1-0686National Science Foundation Grant MIP 95-02885U.S. Navy - Office of Naval Research Grant N00014-96-1-0930National Defense Science and Engineering FellowshipU.S. Air Force - Office of Scientific Research Grant F49620-96-1-0072U.S. Navy - Office of Naval Research Grant N00014-95-1-0362National Science Foundation Graduate Research FellowshipAT&T Bell Laboratories Graduate Research FellowshipU.S. Army Research Laboratory Contract DAAL01-96-2-0002National Science Foundation Graduate FellowshipU.S. Army Research Laboratory/Advanced Sensors Federated Lab Program Contract DAAL01-96-2-000
A Novel Method for Acoustic Noise Cancellation
Over the last several years Acoustic Noise Cancellation (ANC) has been an active area of research and various adaptive techniques have been implemented to achieve a
better online acoustic noise cancellation scheme. Here we introduce the various adaptive techniques applied to ANC viz. the LMS algorithm, the Filtered-X LMS algorithm, the Filtered-S LMS algorithm and the Volterra Filtered-X LMS algorithm and try to understand their performance through various simulations. We then take up the problem of cancellation of external acoustic feedback in hearing aid. We provide three different models to achieve the feedback cancellation. These are - the adaptive FIR Filtered-X LMS, the adaptive IIR LMS and the adaptive IIR PSO models for
external feedback cancellation. Finally we come up with a comparative study of the performance of these models based on the normalized mean square error minimization provided by each of these feedback cancellation schemes
Digital Signal Processing Research Program
Contains table of contents for Section 2, an introduction, reports on twenty-one research projects and a list of publications.U.S. Navy - Office of Naval Research Grant N00014-93-1-0686Lockheed Sanders, Inc. Contract P.O. BY5561U.S. Air Force - Office of Scientific Research Grant AFOSR 91-0034National Science Foundation Grant MIP 95-02885U.S. Navy - Office of Naval Research Grant N00014-95-1-0834MIT-WHOI Joint Graduate Program in Oceanographic EngineeringAT&T Laboratories Doctoral Support ProgramDefense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research Grant N00014-89-J-1489Lockheed Sanders/U.S. Navy - Office of Naval Research Grant N00014-91-C-0125U.S. Navy - Office of Naval Research Grant N00014-89-J-1489National Science Foundation Grant MIP 95-02885Defense Advanced Research Projects Agency/U.S. Navy Contract DAAH04-95-1-0473U.S. Navy - Office of Naval Research Grant N00014-91-J-1628University of California/Scripps Institute of Oceanography Contract 1003-73-5
Optimal Binaural LCMV Beamforming in Complex Acoustic Scenarios: Theoretical and Practical Insights
Binaural beamforming algorithms for head-mounted assistive listening devices
are crucial to improve speech quality and speech intelligibility in noisy
environments, while maintaining the spatial impression of the acoustic scene.
While the well-known BMVDR beamformer is able to preserve the binaural cues of
one desired source, the BLCMV beamformer uses additional constraints to also
preserve the binaural cues of interfering sources. In this paper, we provide
theoretical and practical insights on how to optimally set the interference
scaling parameters in the BLCMV beamformer for an arbitrary number of
interfering sources. In addition, since in practice only a limited temporal
observation interval is available to estimate all required beamformer
quantities, we provide an experimental evaluation in a complex acoustic
scenario using measured impulse responses from hearing aids in a cafeteria for
different observation intervals. The results show that even rather short
observation intervals are sufficient to achieve a decent noise reduction
performance and that a proposed threshold on the optimal interference scaling
parameters leads to smaller binaural cue errors in practice.Comment: To appear in Proc. IWAENC 201
Recovering Multiplexing Loss Through Successive Relaying Using Repetition Coding
In this paper, a transmission protocol is studied for a two relay wireless
network in which simple repetition coding is applied at the relays.
Information-theoretic achievable rates for this transmission scheme are given,
and a space-time V-BLAST signalling and detection method that can approach them
is developed. It is shown through the diversity multiplexing tradeoff analysis
that this transmission scheme can recover the multiplexing loss of the
half-duplex relay network, while retaining some diversity gain. This scheme is
also compared with conventional transmission protocols that exploit only the
diversity of the network at the cost of a multiplexing loss. It is shown that
the new transmission protocol offers significant performance advantages over
conventional protocols, especially when the interference between the two relays
is sufficiently strong.Comment: To appear in the IEEE Transactions on Wireless Communication
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