基于统计模型实现语音信号有声/无声检测的研究

基于语音信号短时平稳性以及语音信号和噪声的统计模型 ,提出了一种语音信号有声 /无声的检测方法 .该方法可对所有语音短时帧更新噪声参数的估值 ,因而提高了检测的准确性 .根据噪声参数以及语音和噪声的统计特性定义了似然比 ,确定了有声 /无声的判别准则 .研究了判别阈值、平滑因子等参数以及缓变非平稳背景噪声对检测结果的影响 .实验结果表明 ,即使背景噪声具有缓变特性 ,利用该方法仍可得到良好的检测结果 .对不同的应用 。

一种基于四阶统计量的语音有声/无声检测技术

语音有声/无声检测是影响语音增强和识别性能的一个关键因素,提出一种鲁棒的基于四阶统计量的语音有声/无声检测技术。利用语音信号的振幅谱是超高斯分布的特性,对每一帧语音信号的振幅谱,计算其四阶统计量,用来度量其超高斯性。结合该帧语音信号的能量,使用一个简单的阈值分类器,实现语音"无声"和"有声"期的检测。所提出的语音有声/无声检测技术,经实验证明具有很好的效果。

一种MMSE语音增强算法的研究与实现

介绍了单话筒采集条件下基于语音短时对数谱的最小均方误差(MMSE-LSA)估计的语音增强算法,以及语音帧和噪声帧判别的有声/无声检测方法。将语音信号的相位提取后存储起来,然后对纯净语音的短时对数谱作最小均方误差估计,处理后的语音由估计得到的幅度谱和存储的相位重建。试验证明MMSE-LSA的增强效果很好,尤其在信噪比低时更为明显。

声发射技术在制造过程监控中的应用

本文在多年来研究声发射技术和过程监控的基础上，论述了制造过程中声发射信号及其监控装置的特点，介绍了刀具状态、切屑形态和磨削接触监测、监控原理及监控仪的结构。

基于DSP的音频会议信号合成算法研究

介绍数字音频合成和回波抵消的基本原理,提供了一种基于DSP的自适应回波抵消和归一化定标实现算法。仿真实验结果证实了该信号合成算法的合理性。实践中使用该算法能够达到很好的音频会议信号合成效果。

通讯系统中语音信号合成算法研究

要实现通讯系统中必备的音频会议功能,数字音频合成和声反馈抵消是音频会议处理中必不可缺的,其算法决定了会议的效果.文章介绍数字音频合成和回波抵消的基本原理,提供了一种基于DSP的自适应回波抵消和归一化定标实现算法.仿真实验的结果证实了该信号合成算法的合理性.实践中使用该算法能够达到很好的音频会议信号合成效果.

基于实时噪声估计的语音增强方法

语音增强的目的是为了在保持语音可懂度和清晰度的前提下,尽可能地从带噪语音中提取需要的纯净语音,从而改善其质量,在实际应用中还需要对背景噪声进行预估。该文将实时噪声估计与维纳滤波法相结合,提出了一套简易有效的语音增强方案,在语音帧阶段对噪声功率谱进行平滑处理,使噪声估计更适合于维纳滤波,并配合传统的过减法以补偿估计引入的误差。Matlab实验表明在较低信噪比下,这种方法使得语音的信噪比有较大的提高,语音增强效果十分明显。

Phase aberration correction in ultrasonic phased array non-destructive testing systems

Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in various fields, the problem of phase aberrations in the process of NDT testing is considered. The technique of cross-covariance for phase aberration correction is presented. The performance of the technique for phase aberration correction is tested by means of echo signals obtained in practical non-destructive testing experiment. The results show that the technique has the better accuracy of phase correction.

基于GFCC和能量算子倒谱的语种识别

为了提高低信噪比下语种识别的准确率,引入一种新的特征提取融合方法.在前端加入有声段检测,并基于人耳听觉感知模型提取伽玛通频率倒谱系数(Gammatone Frequency Cepstrum Coefficient,GFCC)特征,通过主成分分析对特征进行压缩、降噪,融合每个有声段的Teager能量算子倒谱参数,通过高斯混合通用背景模型进行语种识别验证.实验结果表明,在信噪比为-5~0 dB时,相对于基于对数梅尔尺度滤波器组能量特征方法,融合特征集方法对5种语言的识别率,分别提升了23.7%~34.0%,其他信噪比等级下识别率也有明显的提升.

A New Method for Detecting Internal Defects in Composite Materials Based on Time of Flight

Carbon-fiber reinforced polymer composites have been widely used to achieve the light-weighted design and high performance due to superior performance. Internal defects in the composite materials are the main factors that determine their performance,which makes reliable and effective detection methods of internal defects essential. Nondestructive testing(NDT)methods are the most widely-used way due to their tremendous advantages. Though the theoretical background is found,experimental results could be quite complicated and confusing,especially for composite materials with complex defects characteristics. In this paper,experimental study on internal defects in composite materials based on the time of flight(ToF)are investigated. The Gaussian echo model and the parameter estimation methods are established to build a theoretical model for measurements. Then,the distance amplitude correction(DAC)method is proposed to effectively improve the signal-to-noise ratio(SNR)and to reduce distortion of the signal during measurements. Finally,the ToF is adopted to determine depth of internal defects. Experiment study is conducted to investigate the porosity defects and the anti-impact performance of composite materials,as well as defects in objects with various thicknesses. Experimental results show that the proposed method is quite helpful for obtaining the intuition and deep understanding of internal defects,thus contributing to the determination of product performance and its improvement.

Nonlinear ultrasonic detection for curing properties of the liner

The relationship between ultrasonic nonlinearity and microstructure of the liner was studied during the whole curing process by ultrasonic transmission method and infrared spectroscopy.Nonlinearity of input instrumentation was minimized by the natural filtering effect of piezoelectric discs and the maximum excitation energy was acquired simultaneously so as to improve the accuracy of the measuring data.The experimental results indicate that in the liner curing reaction at40℃ultrasonic nonlinearity parameter decreases gradually after a sharp decline,which is consistent with the outcome of infrared spectroscopy as the curing degree increases.The research suggests an effective nondestructive approach to detect the curing properties of the liner in a nonlinear ultrasonic way.

Spectrum Handoff Scheme Based on Recommended Channel Sensing Sequence

We consider the spectrum handoff delay of a Secondary User(SU)in cognitive radio networks.We propose a spectrum handoff scheme based on Recommended Channel Sensing Sequence(RCSS),which aims to optimise the spectrum handoff delay subject to the sensing reliability and link maintenance constraints.There are two cases that should be considered:1)the SU performs spectrum handoff successfully during the current frame,and 2)the SU successfully performs the spectrum handoff using several frames.We develop a dynamic programming algorithm for RCSS to identify the optimal sensing sequence for the first case,and an updating algorithm for RCSS to improve the handoff performance for the second case.The numerical results confirm that the proposed RCSS handoff scheme can achieve better handoff delay performance than others when the received signal-to-noise ratios of the Pus' signals on different channels are non-identical.

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge

The ultrasonic computed tomography （USCT） method is derived from the basic principles of X-ray section scanning. This method records the arriving times of ultrasonic wave between the probes and the sources to ealculate the elastic wave velocity values in the section using the arrival times. Through analyzed the distribution Of elastic wave velocity in aim area, the information of the strength and the homogeneity of the investigated zone could be got indirectly. The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member. Compared with other exploration methods, this method is more efficient and accurate.

一种改进的基于谱熵实时噪声估计的谱减法

语音增强的目标是从含有噪声的语音信号中提取尽可能纯净的原始语音.在实际应用中,需要对背景噪声进行预估计,以达到改善语音质量.目前常用的语音增强方式是谱减法,但由于该算法在低信噪比环境下的效果较差,所以限制了其应用范围.该文将实时噪声估计同谱减法相结合,针对谱减法在低信噪比下效果不明显的缺点,给出一种新的语音增强方案.该方案的目的是优化传统谱减法的性能,对噪声进行更为准确的实时估计;该方案的特点就是利用谱熵对噪声进行估计,通过谱熵估计每一帧语音的噪声,再利用谱减法达到降噪的目的.实验结果表明,该方法与传统的谱减法相比,在低信噪比环境下均能得到较好的去噪效果.