Nonlinear Acoustic Echo Canceller to Combat Sigmoid-Type Nonlinearities Under Noisy Environment
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Nonlinear Acoustic Echo Canceller to Combat Sigmoid‑Type Nonlinearities Under Noisy Environment Amit Kumar Kohli1 · Jashu Sharma1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper presents a nonlinear-acoustic-echo-cancellation (NAEC) technique to tackle sigmoid-type nonlinearities under noisy environment. The nonlinear echo in acoustic systems is inevitable due to the inherent nonlinear characteristics of amplifiers and/or loudspeakers, which deteriorates the quality of speech as well as audio signal reception. Here, the sigmoid-type nonlinearity is modelled by incorporating two control parameters, which determine the shaping- and clipping-parameter values of the saturation curve at a particular room temperature. These control parameters are adjusted by utilizing the variable-stepsize (VSS) least-mean-square (LMS) algorithm to enhance the convergence rate and tracking capability of presented NAEC. Furthermore, the impulse response of a room (indoor channel) in the acoustic echo path is modelled as a tap-delay-line finite-impulse-response filter, whose tap-coefficients are estimated by utilizing a modified recursive-least-squares (RLS) algorithm (involving the noise statistics) at the different values of signal-to-noiseratio (SNR), when correlated as well as uncorrelated input signals are processed. Simulation results demonstrate the efficiency and efficacy of above mentioned adaptive NAEC technique using the VSS-LMS and modified RLS algorithms in terms of the high convergence rate as well as high value of echo-return-loss-enhancement (ERLE) factor. Both the elevating value of shaping-parameter (i.e., increasing nonlinearity level) and the alleviating value of SNR adversely affect the performance of all NAECs. However, the VSS-LMS and modified RLS algorithm based presented adaptive NAEC outperforms the traditional VSS-LMS and normalized-least-mean-square (NLMS) algorithm based NAEC under similar conditions. Keywords Acoustic-echo-cancellation (AEC) · Sigmoid function · VSS-LMS · NLMS · RLS · ERLE
* Amit Kumar Kohli [email protected] Jashu Sharma [email protected] 1
Department of Electronics and Communication Engineering, Thapar Institute of Engineering and Technology, Patiala, Punjab 147004, India
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A. K. Kohli, J. Sharma
1 Introduction The nonlinear acoustic distortion is inevitable under the large-signal situation in case of power amplifier and/or loudspeaker, which impairs the performance of linear acousticecho-cancellers (AECs). The nonlinear cone as well as uneven magnetic flux density in the loudspeaker establish nonlinear distortion at the large cone displacement levels [1]. However, it is tedious to design a unified paradigm that can describe almost every type of nonlinear distortion. The linear AEC fails to perform well, when nonlinear echo paths come into picture. Adaptive nonlinear techniques are required to achieve adequate echo cancellation [1]. But, the performance of nonlinear-acoustic-echo-cancellers (NAECs) is highly d
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