6 results for Abdulla, Waleed H.

  • On the stochastic modeling and analysis of FxLMS adaptation algorithm

    Ardekani, Iman; Abdulla, Waleed H. (2013)

    Journal article
    Unitec

    This study represents a stochastic model for the adaptation process performed on adaptive control systems by the filtered-x least-mean-square (FxLMS) algorithm. The main distinction of this model is that it is derived without using conventional simplifying assumptions regarding the physical plant to be controlled. This model is then used to derive a set of closed-form mathematical expressions for formulating steady-state performance, stability condition and learning rate of the FxLMS adaptation process. These expressions are the most general expressions, which have been proposed so far. It is shown that some previously derived expressions can be obtained from the proposed expressions as special and simplified cases. In addition to computer simulations, different experiments with a real-time control setup confirm the validity of the theoretical findings.

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  • Stability of residual acoustic noise variance in active control of stochastic noise

    Ardekani, Iman; Abdulla, Waleed H. (2013)

    Conference paper
    Unitec

    This paper concerns about the theoretical stability of the adaptation process performed by the Filtered-x Least Mean Square (FxLMS) algorithm in active control of acoustic noise. A dynamic model for the Variance of Residual Acoustic Noise (VRAN) is developed and it is shown that the stability of this model is a sufficient condition for the stability of the adaptation process. The basic rules governing the VRAN root locus are developed, based on which an upper-bound for the adaptation step-size is derived. This upper-bound can apply to a general case with an arbitrary secondary path, unlike the traditional upper-bound used in adaptive filter theory, which was derived only for pure delay secondary paths.

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  • Efficient FXLMS algorithm with simplified secondary path models.

    Ardekani, Iman; Sharifzadeh, Hamid Reza; Rehman, Saeed; Abdulla, Waleed H. (2015)

    Conference paper
    Unitec

    his paper extends the existing work on the root locus analysis of FxLMS algorithm by considering secondary path modeling errors. Rules for sketching FxLMS root locus are set out. An analytic convergence condition is then derived from the root locus plot. A deliberately-misaligned secondary path model is proposed to be used as the data preparation filter in the FxLMS algorithm. The proposed filter increases the computational efficiency of the algorithm, without changing its convergence behavior. The theoretical results are verified in practice by busing an experimental system.

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  • Remote FxLMS algorithm for active control of sound in remote locations

    Ardekani, Iman; Abdulla, Waleed H.; Rehman, Saeed (2014)

    Conference paper
    Unitec

    Available adaptive control algorithms can only create a silent point at the locations of an error microphone. In this case, the error microphone occupies a part of the zone of quiet established around the silent point, resulting in an ineffective use of space in the zone of quiet. This paper develops a novel adaptive control algorithm for active control of sound in remote locations rather than the locations of error microphones. It establishes a link between the performance of the FxLMS adaptive algorithm in the digital control domain and the performance of the active noise control mechanism in the acoustic domain. The transfer function of an optimal controller that can minimize the acoustic pressure in a location away from the error microphone is first derived. For the realization of the proposed controller, an adaptive algorithm, called Remote FxLMS is then developed. Different computer simulations are used to show the efficiency of the proposed algorithm.

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  • Speech Enhancement by Multichannel Crosstalk Resistant ANC and Improved Spectrum Subtraction

    Zeng, Qingning; Abdulla, Waleed H. (2006)

    Journal article
    The University of Auckland Library

    An open access copy of this article is available and complies with the copyright holder/publisher conditions. A scheme combining multichannel crosstalk resistant adaptive noise cancellation (MCRANC) algorithm and improved spectrum subtraction (ISS) algorithm is presented to enhance noise carrying speech signals. The scheme would permit locating the microphones in close proximity by virtue of using MCRANC which has the capability of removing the crosstalk effect. MCRANC would also permit canceling out nonstationary noise and making the residual noise more stationary for further treatment by ISS algorithm. Experimental results have indicated that this scheme outperforms many commonly used techniques in the sense of SNR improvement and music effect reduction which is an inevitable byproduct of the spectrum subtraction algorithm.

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  • Adaptive active control of free space acoustic noise

    Ardekani, Iman; Abdulla, Waleed H. (2013)

    Conference paper
    Unitec

    This paper concerns adaptive active control of acoustic noise in free space. Conventional adaptive active noise control algorithms are efficient in acoustic ducts or headphones; however, they are very sensitive when being used in free space. An efficient adaptive active noise control algorithm for free space noise is developed based on analyzing noise field in a volumetric zone around the error microphone. The traditional algorithm and the proposed algorithm are fully implemented by using a high performance embedded controller. The implemented setup is then used for active control of acoustic noise in free space. Different experiments show that the traditional active noise control algorithm is not stable when being used for free space noise; however, the proposed algorithm is stable and attenuates noise in free space by about 15 dB.

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