Time distributed update of the NLMS algorithm coefficients for Acoustic Echo Cancellers (original) (raw)
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ACOUSTIC ECHO CANCELLATION FOR HANDS-FREE APPLICATIONS USING ADAPTIVE FILTERS
Acoustic Echo Cancellation (AEC) has become an essential and well known enabling technology for hands-free communication where acoustic echo occurs due to echo coupling between loudspeaker and the microphone. This acoustic echo makes the communication difficult and would make the acoustic system unstable. Therefore to address that issue a real time implementation of echo cancellation system utilizing a Digital Signal Controller (DSC) based on NLMS algorithm is proposed here. In addition to that, acoustic cancellation algorithm is implemented on a running PC with the help of the MATLAB software.
Echo Cancellation in Audio Signal using LMS Algorithm
2001
Acoustic echo cancellation is a common occurrence in today’s telecommunication systems. It occurs when an audio source and sink operate in full duplex mode; an example of this is a hands-free loudspeaker telephone. The signal interference caused by acoustic echo is distracting to both users and causes a reduction in the quality of the communication. This paper focuses on the use of adaptive filtering techniques to reduce this unwanted echo, thus increasing communication quality. Adaptive filters are a class of filters that iteratively alter their parameters in order to minimize a function of the difference between a desired target output and their output. In the case of acoustic echo in telecommunications, the optimal output is an echoed signal that accurately emulates the unwanted echo signal. This is then used to negate the echo in the return signal. This paper examines various techniques and algorithms of adaptive filtering, employing discrete signal processing in MATLAB.
Acoustic Echo Cancellation using LMS Algorithm
International Journal of Broadband Cellular Communication, 2016
One of the core technologies these days in digital signal processing which find numerous application areas in science as well as in industry is adaptive filtering. Adaptive filtering techniques are used in a wide range of applications, including adaptive equalization, echo cancellation, adaptive noise cancellation, and adaptive beam forming. In today's telecommunication system, acoustic echo cancellation is a common occurrence. The signal interference caused by acoustic echo is distracting the users and causes a reduction in the quality of the voice communication. Echo cancellers are very successful these days and almost no echo can be perceived while using telephones. The present work focuses on the LMS algorithm to reduce the unwanted echo which results in improving communication quality. LMS algorithm is a type of adaptive filter algorithm and is used to determine the minimum mean square error and is based on steepest descent method and gradient search technique. Thus in this research work we are going to eliminate noise signal from audio signal using this LMS algorithm. This causes the clear and high quality audio signal as an output signal. Simulation results are presented to support the analysis. They show that the LMS algorithm reduced the echo from the input noisy signal by 40 percent.
2009
In hands-free telephony and in teleconference systems, the main aim is to provide a good free voice quality when two or more people communicate from different places. The problem often arises during the conversation is the creation of acoustic echo. This problem will cause the bad quality of voice signal and thus talkers could not hear clearly the content of the conversation, even thought lost the important information. This acoustic echo is actually the noise which is created by the reflection of sound waves by the wall of the room and the other things exist in the room. The main objective for engineers is the cancellation of this acoustic echo and provides an echo free environment for speakers during conversation. For this purpose, scientists design different adaptive filter algorithms. Our thesis is also to study and simulate the acoustics echo cancellation by using different adaptive algorithms.
Improved variable step-size NLMS adaptive filtering algorithm for acoustic echo cancellation
Digital Signal Processing, 2016
Acoustic echo canceller (AEC) is used in communication and teleconferencing systems to reduce undesirable echoes resulting from the coupling between the loudspeaker and the microphone. In this paper, we propose an improved variable step-size normalized least mean square (VSS-NLMS) algorithm for acoustic echo cancellation applications based on adaptive filtering. The steady-state error of the NLMS algorithm with a fixed step-size (FSS-NLMS) is very large for a non-stationary input. Variable step-size (VSS) algorithms can be used to decrease this error. The proposed algorithm, named MESVSS-NLMS (mean error sigmoid VSS-NLMS), combines the generalized sigmoid variable step-size NLMS (GSVSS-NLMS) with the ratio of the estimation error to the mean history of the estimation error values. It is shown from single-talk and double-talk scenarios using speech signals from TIMIT database that the proposed algorithm achieves a better performance, more than 3 dB of attenuation in the misalignment evaluation compared to GSVSS-NLMS, non-parametric VSS-NLMS (NPVSS-NLMS) and standard NLMS algorithms for a non-stationary input in noisy environments.
The performance study of NLMS algorithm for acoustic echo cancellation
2017 International Conference on Information, Communication, Instrumentation and Control (ICICIC), 2017
We provide the performance Study of NLMS Algorithm for audio echo termination. The AEC (Acoustic Echo Cancellation) has been completed based on their convergence rate, MSE (Mean Square Error), steady state ERLE (Echo Return Loss Enhancement) and computational difficulty. The results explain the NLMS (Normalized Least Mean Square) algorithm comes with increased convergence rate whereas controlling minimal computational difficulty. It may be displayed as permitting the attenuation value along with the integer of replication functions; it's the obvious choice useful for the real location AEC system.
The problem of acoustic echo is well defined in case of hands-free communication.The presence of large acoustic coupling between the loudspeaker and microphone would produce an echo that causes a reduction in the quality of the communication.The solution to this problem is the elimination of the echo with an echo canceller which increases the speech quality and improves listening experience. In this paper, many prominent work done in relation to acoustic echo cancellation (AEC) is discussed and analysed. The existing AEC algorithms are analysed and compared based on their merits and demerits in a time varying echoed environment. It covers the basic algorithms like least mean square (LMS) , normalized least mean square (NLMS) and recursive least square algorithm as well as their modified versions like variable step size NLMS, fractional LMS, Filtered-x LMS, variable tap-length LMS algorithm, multiple sub-filter (MSF) based algorithms, variable tap-length MSF structures etc. Finally, a judicious comparison is presented towards the end of the paper in order to judge the best AEC algorithm in the present time.
A New Adaptive Filter Approach for Acoustic Echo Canceller in Teleconference Systems
A flexible Frequency domain Block Recursive Least Squares (FBRLS) algorithm using the Multi-Delay Filter (MDF) is presented throughout this paper. In term of performances, the MDF-FBRLS adaptive filter introduces smaller block delay and is usually faster and suitable for ideal time-varying system such as an acoustic echo in a teleconference room. The implementation of the FBRLS algorithm using MDF adaptive filter allows reducing the FFT size and consequently optimizing the hardware implementation that could be performed using standard DSP chips. These good performances are achieved by using smaller block size and updating frequently the weight vectors which will reduce the total execution time of the adaptive process. Simulation results show that the MDF-FBRLS algorithm is better than the FBRLS algorithm in terms of the total execution time and the efficiency of the computational complexity.
Implementation of a Low-Cost Acoustic Echo Canceller
Hands-free telephone sets with adaptive echo cancellers need an adaptive loss control in order to guarantee a loss of acoustic echo of about 45 dB (ITU-T Recommendation G.167 (l)). The quality of the speech transmission de- pends on the coupling between the echo canceller and the loss control. In this contribution we present an imple- mentation of a hands-free telephone algorithm, using a low-cost fixed-point DSP which is well suited for integra- tion in consumer devices. It is a well known fact that in realistic environ- ments one cannot achieve, even with the best avail- able DSP's, an echo loss of more than 2&25dB with an adaptive echo canceller. This is due to changes in the echo path, disturbing background noise, limited number of filter taps etc. In order to provide a constant total echo loss of about 45dB, one can use an adaptive loss control. An adaptive loss control estimates whether the local speaker or the far-end speaker is talking and attenu- ates the channel that ...
Acoustic echo cancellation is a common occurrence in today's telecommunication systems. Acoustic echo occurs when a speech signal is reverberated in real environment. Acoustic echo causes the signal interference which is distracting to users and reduces the quality of the communication. This paper focuses on the use of LMS and NLMS algorithms to reduce this unwanted echo in case of stereophonic acoustic echo cancellation, thus increasing the quality of speech.