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Hands-free terminals for speech communication employ adaptive filters to reduce echoes resulting from the acoustic coupling between loudspeaker and microphone. When using a personal computer with commercial audio hardware for teleconferencing, a sampling frequency offset between the loudspeaker output D/A converter and the microphone input A/D converter often occurs. In this case, state-of-the-art echo cancellation algorithms fail to track the correct room impulse response. In this paper, we present a novel least mean square (LMS-type) adaptive algorithm to estimate the frequency offset and resynchronize the signals using arbitrary sampling rate conversion. In conjunction with a normalized LMS-type adaptive filter for room impulse response tracking, the proposed system widely removes the deteriorating effects of a frequency offset up to several Hz and restores the functionality of echo cancellation. 相似文献
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Gudvangen S. Flockton S.J. 《Vision, Image and Signal Processing, IEE Proceedings -》1995,142(1):47-51
ARMA modelling (infinite impulse response filters having both poles and zeros), rather than MA modelling, of acoustic transfer functions is potentially capable of reducing the number of coefficients required to achieve a given level of echo cancellation. The amount of reduction obtainable, however, has received little attention in the literature. To arrive at quantitative figures for the complexity reduction possible, equation error and output error ARMA and MA modelling of acoustic impulse responses are compared experimentally. It is shown, for both fullband and subband implementations, that the potential for reducing the number of coefficients required is small 相似文献
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自适应滤波器在系统辨识、回声消除、信道均衡等领域获得了广泛应用.符号子带自适应滤波器(Sign Subband Adaptive Filter,SSAF)具有较强的抗脉冲干扰能力,但当输入信号受到噪声干扰时,其对未知系统系数向量的估计会产生偏差.为了解决上述问题,本文基于无偏估计准则,提出了一种偏差补偿符号子带自适应滤波器(Bias-Compensated Sign Subband Adaptive Filter,BC-SSAF).为了解决定步长自适应滤波器需要在收敛速度和稳态失调之间进行折中的问题,本文采用随机梯度法来更新正则化参数,提出了变正则化参数偏差补偿符号子带自适应滤波器(Variable Regularization Bias-Compensated Sign Subband Adaptive Filter,VR-BC-SSAF).仿真结果验证了BC-SSAF和VR-BC-SSAF性能的优越性. 相似文献
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《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(10):1056-1060
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The adequateness of IIR models for acoustic echo cancellation is a long-standing question, and the answers found in the literature are conflicting. We use the results from rational Hankel norm and least-squares approximation, and we recall a test that provides a priori performance levels for FIR and IIR models. We apply this test to the measured acoustic impulse responses. Upon comparing the performance levels of FIR and IIR models with the same number of free parameters, we do not observe any significant gain from the use of IIR models. We attribute this phenomenon to the shape of the energy spectra of the acoustic impulse responses so tested, which possess many strong and sharp peaks. Faithful modeling of these peaks requires many parameters, irrespective of the type of the model 相似文献
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Tools are presented which enable the practitioner to efficiently design all-pass based, highly selective low-pass power symmetric-infinite impulse response (PS-IIR) filters which are well suited for sub-band decomposition in applications such as multirate acoustic echo cancellation (MAEC) 相似文献
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In acoustic echo cancellation (AEC), the sparseness of impulse responses can vary over time or/and context. For such scenario, the proportionate normalized subband adaptive filter (PNSAF) and μ-law (MPNSAF) algorithms suffer from performance deterioration. To this end, we propose their sparseness-measured versions by incorporating the estimated sparseness into the PNSAF and MPNSAF algorithms, respectively, which can adapt to the sparseness variation of impulse responses. In addition, based on the energy conservation argument, we provide a unified formula to predict the steady-state mean-square performance of any PNSAF algorithm, which is also supported by simulations. Simulation results in AEC have shown that the proposed algorithms not only exhibit faster convergence rate than their competitors in sparse, quasi-sparse and dispersive environments, but also are robust to the variation in the sparseness of impulse responses. 相似文献
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Teleconferencing systems and hands-free mobile terminals use acoustic echo cancellation (AEC) for high-quality full-duplex speech communication. The problem of aliasing in subband AEC is addressed. Filter banks with implicit notch filtering are derived from cascaded power symmetric-infinite impulse response (CFS-IIR) filters. It is shown that adaptive filters used with these filter banks must be coupled via continuity constraints to reduce the aliasing in the residual echo. A continuity constrained NLMS algorithm is therefore proposed and evaluated 相似文献
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An acoustic echo canceller with sub-band noise cancelling that employs a cascade configuration is proposed. The adaptation control adopted to match the occurrence of intermittent speech/echo and continuous room noise using the NLMS algorithm is very effective in echo and noise cancellation. Hardware is implemented and its performance evaluated through experiments. The noise cancellation significantly enhances overall echo-cancellation performance.<> 相似文献
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文中提出了一种新的多相位子带自适应回声消除系统。在子带内进行自适应滤波对建模长度比较长的脉冲响应特别有效,同时由于仿射投影算法具有预白化的作用,它同样也具有改善滤波器收敛性能的功能。该系统集中了多相子带自适应滤波和仿射投影算法的优点,结合了子带内的双端检测算法,使得系统在临界采样的情况下能进行稳定有效的工作。实验表明:该系统对于语音信号和强相关信号都表现出了良好的性能。 相似文献
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Design and performance of adaptive systems based on structured stochastic optimization strategies 总被引:2,自引:0,他引:2
The theory and design of linear adaptive filters based on FIR filter structures is well developed and widely applied in practice. However, the same is not true for more general classes of adaptive systems such as linear infinite impulse response adaptive filters (MR) and nonlinear adaptive systems. This situation results because both linear IIR structures and nonlinear structures tend to produce multi-modal error surfaces for which stochastic gradient optimization strategies may fail to reach the global minimum. After briefly discussing the state of the art in linear adaptive filtering, the attention of this paper is turned to MR and nonlinear adaptive systems for potential use in echo cancellation, channel equalization, acoustic channel modeling, nonlinear prediction, and nonlinear system identification. Structured stochastic optimization algorithms that are effective on multimodal error surfaces are then introduced, with particular attention to the particle swarm optimization (PSO) technique. The PSO algorithm is demonstrated on some representative IIR and nonlinear filter structures, and both performance and computational complexity are analyzed for these types of nonlinear systems. 相似文献
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针对水声信道中窄带信号的多途时延估计问题,本文在对复倒谱时延估计方法进行研究的基础上,提出了一种基于对数域同态滤波的时延估计算法.结合复倒谱与同态滤波思想,将接收的窄带信号首先变换到对数域,然后与本地存储的信号进行谱减法,再对相减后的信号进行滤波以消除残余的信号与噪声成分,最后将其恢复到时域以获取多途时延估计.与传统的匹配滤波/相关处理以及复倒谱分析方法相比,本文算法具有时延估计精度高、噪声抑制能力较强等特点.仿真与湖试数据处理结果证明了该方法的有效性. 相似文献
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双基地逆合成孔径(ISAR)成像中,一维距离像的分辨率因双基地角的存在而下降,为解决此问题,研究了双基地ISAR的一维距离成像算法。在分析复基带回波稀疏特性的基础上,将一维距离像的生成问题转化为噪声环境下信号的稀疏分解问题。利用可任意调节的时延单元构建冗余基,基于L曲线准则估计正则参数,最后利用推广的正则化FOCUSS算法估计复基带回波的稀疏分解系数,并据此生成目标的一维距离像。一维距离像分辨率取决于构建稀疏分解冗余基的延时单元,据此解决了双基地角对距离分辨率的限制问题,仿真实验验证了算法的有效性。 相似文献