应用于增量式光电编码器的相关自适应滤波方法

为了改善增量式光电编码器的莫尔条纹光电信号质量,降低主计数信号中高次谐频的影响,提高信噪比达到输出稳定的正弦波形,本文深入地研究了莫尔条纹光电信号中的高频信号和噪音信号产生的原因及其相关自适应滤除方法.从宏观和微观两个方案分析光栅副的屏函数,研究莫尔条纹光电信号输出波形的不确定原因,并且提出采用相关自适应滤波方法将高频信号滤除保留原有基频信号.从相关自适应滤波的数学模型论证和推导该相关自适应滤波过程并讨论其自适应性.指出在设计该自适应滤波电路时需要重视的几个关键指标及其影响效果,完成相关自适应滤波的有效性分析.相关自适应滤波效果等价于一个中心频率为基频的窄带带通滤波器,当基频随机变化时其通带也会随之改变.通过相关自适应滤波技术较好地滤除计数信号中除基频外所有高频分量和放大电路所引入的加性高斯白噪音.实验证明：莫尔条纹光电信号的失真度被降低8倍相关自适应滤波方法能使莫尔条纹光电输出波形趋近于标准正弦波,获得更高的信噪比.     

畸变波前相位校正效果分析

 以随机相位屏构造波前畸变相位,运用高通滤波的方法模拟变形镜对光束波前畸变相位的校正作用,模拟分析了畸变波前的相位校正效果,定量分析了校正效果与低频相位畸变和高频相位畸变之间的关系,并进一步讨论了变形镜的校正位置对校正效果的影响。研究结果表明:对于给定单元尺寸的变形镜,随着畸变波前中高频相位畸变所占比例的增大,经校正后的远场光束质量明显降低,校正效果也越来越差。此外,光学变形镜所在位置对校正效果存在明显影响,校正效果随校正位置的变化呈现出起伏变化。     

Problems and pitfalls of electroglottography

The popularity and usefulness of the electroglottograph (EGG) has increased remarkably since its introduction over a decade ago. It has been used to measure fundamental frequency of phonation, fundamental frequency perturbation, details of the vocal fold vibratory cycle, as well as to provide an indication of laryngeal vertical movement. It has also been used with a variety of speech and voice disorders. The EGG is not without its limitations and problems. Some of these are found in the electronic designs of specific instruments, whereas other problems are related to subject characteristics, the placement of the electrodes, electrode symmetry, and subject/instrument interaction. This article explores some of these concerns, primarily from the perspective of two individuals who have used the EGG extensively with children, men and women, voice patients, stutterers, and neurologically impaired persons. Some of the concerns to consider and pitfalls to avoid in the interpretation and measurement of EGG signal are discussed.     

Perturbation-free measurement of the harmonics-to-noise ratio in voice signals using pitch synchronous harmonic analysis.

The measurement of the harmonics-to-noise ratio (HNR) in speech signals gives an indication of the aperiodicity of the speech waveform. This may be due to the presence of jitter, shimmer, additive noise, waveshape change, or some unknown combination of these factors. In order to estimate the HNR as a measure of the additive noise component only, the contaminating effects of the other contributory components must first be removed. A pitch synchronous harmonic analysis is proposed to overcome this problem. The procedure takes advantage of the time scale compression-frequency expansion property of the Fourier series in order to eliminate jitter and shimmer. Successive spectra are added by harmonic number as opposed to frequency location, and perturbation is removed due to the fact that the relative heights of the harmonic components remain the same for scaled signals. The technique is examined on synthetically generated voice signals. A discussion of the results is given in terms of human voice signals, characterization of jitter, vocal tract filtering effects, perturbation mechanisms, nonlinear dynamics, and the possibility of developing the method for use with inverse filtering strategies.     

光学空间滤波过程的计算机仿真

提出了一种利用MATLAB软件并通过计算机仿真光学空间滤波实验过程的新方法.其特点是:既可以随意改变所设计滤波器的参量,又可以对输入图象进行振幅、相位或复合滤波,并且可实现傅里叶变换频谱中相位信息的提取、存储和利用,因而能够完成一般光学实验中往往难以实现的某些操作.并分别给出了网格滤波、低通、高通及相位滤波等仿真实验结果.这种仿真实验给光学滤波器的设计和图象处理带来很大方便,同时也为相关器件的设计提供了一条新的途径.     

Clinical applications of electroglottography

Electroglottography (EGG) is a method to monitor the vibrations of the vocal folds by measuring the varying impedance to a weak alternating current through the tissues of the neck. The paper is an attempt to give a state-of-the-art report of how electroglottography is used in the clinic. It is based on a search of the pertinent literature was well as on an inquiry to 17 well known specialists in the field. The EGG techniques are described and limitations to the method are pointed out. Attempts to document voice quality by EGG are recognized and computerized methods to obtain information about vibratory perturbations and/or the vibratory frequency of the vocal folds are described. The author's personal conclusion is that the EGG signal is especially well suited for measurements of the glottal vibratory period. In the clinic such measurements are useful for periodicity analysis, as a basis for recording intonation contours, and to establish the characteristics of the voice fundamental frequency.     

Spectral characterization of jitter, shimmer, and additive noise in synthetically generated voice signals

Alteration of the harmonic structure in voice source spectra, taken over at least two periods of the waveform, may occur due to the presence of fundamental frequency (f0) perturbation, amplitude perturbation, additive noise, or changes within the glottal source signal itself. In order to make accurate inferences regarding glottal-flow dynamics or perceptual evaluations based on spectral measurements taken from the acoustic speech waveform, investigation of the spectral features of each aperiodic component is required. Based on a heuristic development involving a consideration of the partial sum of the Fourier series taken for two periods of a jittered, shimmered, and (additive, random) noise-contaminated signal, the corresponding spectral characteristics are hypothesized. Subsequent to this, the Fourier series coefficients are calculated for the two periods in order to test the hypotheses. Definite spectral differences are found for each aperiodic component; based on these findings differential quantitative spectral measurements are suggested. Further supportive evidence is obtained through use of Fourier transform and periodogram-averaged calculations. The analysis is carried out on synthetically generated glottal-pulse waveforms and on radiated speech waveforms. A discussion of the results is given in terms of voice aperiodicity in general and in terms of their implication for future studies involving human voice signals.     

空腔中B-dot的低频响应特性北大核心CSCD

针对空腔中B-dot的频响特性开展了分析。当频率低于一定值时,安装在空腔中的B-dot探头的输出信号存在低频分量增益,可以用一个"负时间常数的RC高通滤波器"描述其频响特性,其本质是低频段为增益的高通滤波器。采用不同等效频率的RLC回路连接安装B-dot的传输线,开展了B-dot探头低频响应的实验研究,结果表明,被测信号等效频率不同时,标定得到的磁通穿透特征时间常数以及互感系数有所不同。因此,为得到正确的修正系数,应当使标定波形的等效频率尽量接近实测波形。     

Limits to the role of a common fundamental frequency in the fusion of two sounds with different spatial cues

Two experiments establish constraints on the ability of a common fundamental frequency (F0) to perceptually fuse low-pass filtered and complementary high-pass filtered speech presented to different ears. In experiment 1 the filter cut-off is set at 1 kHz. When the filters are sharp, giving little overlap in frequency between the two sounds, listeners report hearing two sounds even when the sounds at the two ears are on the same F0. Shallower filters give more fusion. In experiment 2, the filters' cut-off frequency is varied together with their slope. Fusion becomes more frequent when the signals at the two ears share low-frequency components. This constraint mirrors the natural filtering by head-shadow of sound sources presented to one side. The mechanisms underlying perceptual fusion may thus be similar to those underlying auditory localization.     

不同滤波方法对揭示全球海洋条带结构的比较

海洋条带结构是近年物理海洋学研究的一个新热点. 在海洋中, 条带结构往往被大尺度环流过程所掩盖. 把这种隐蔽的海水运动现象显现出来的办法是对时间平均的速度场进行空间滤波. 利用全球简单海洋资料同化分析系统资料和中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室的气候系统海洋模式模拟数据对三种一维滤波方法进行了比较, 分别是常用的高斯和汉宁滤波方法, 以及本文引入的切比雪夫滤波方法. 结果表明, 尽管三种方法均可获得条带结构, 但以切比雪夫方法为最佳; 另外, 设计高通滤波器时需设定截断频率, 而它的选定取决于对具体数据的频谱分析, 当选取的归一化的截断频率值在0.1和0.4之间时, 可以有效地揭示出条带结构在全球海域内的分布. 因此本文的研究方法为海洋条带结构的深入研究提供了一个有力工具.     

Time normalization in voice analysis.

The harmonics-to-noise ratio (HNR) has been widely accepted for quantifying the irregular or noise component of voice. HNR, however, is usually inflated by cycle-to-cycle variations of fundamental frequency period because zero padding is used for time normalization of the wavelet. In this study, a new method was developed for analyzing waveform perturbations of voice. In this method, noise components of voice were calculated from the discrepancies between wavelets after they had been optimally aligned in time. The optimal time normalization of wavelets was accomplished using procedures of dynamic time warping (DTW). This method was evaluated using both synthetic and natural voices, and significant reductions in noise were obtained. The harmonics-to-noise ratio obtained using DTW for time normalization was also shown to be independent of fundamental frequency perturbations.     

Zero-frequency elimination using the filtering characteristics of a volume grating

Angular selectivity of a volume grating has been exploited to generate a high-pass filtering function that cuts off the zero frequency and attenuates the low frequencies. The filter can be used for the edge enhancement of amplitude and phase objects. Partially coherent light is used in the reading process.     

Image enhancement by the modified high-pass filtering approach

We demonstrate a brand-new method for image enhancement by using a modified high-pass filtering approach. Some specific spatial frequencies are selectively magnified by exaggerating the local visibility of an image. Then a high-pass filter is employed to adjust those critical frequencies. The enhanced final image has well-sharpened fine characteristics.     

傅里叶变换轮廓术中滤波窗方位选择研究

在傅里叶变换轮廓术频域滤波过程中通常采用不对称的汉宁窗滤波窗来提取基频信号,当投影呈二维变化的光栅条纹时,采用的滤波窗长短轴方向和载频方向不吻合,会导致被测物体的部分高频信息丢失,从而影响相位展开的难易程度和系统测量的精度。分析比较物体高度的分布与频谱的关系,通过旋转滤波窗使其短轴方向与载频方向一致,可以保留物体的高频信息,降低相位展开的复杂度,提高测量的精确度。计算机模拟和实物实验结果表明滤波窗旋转滤波可以避免相位展开在物体高度突变处的出错,有效地提高测量精度。     

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针对HL-2A装置极向场电源晶闸管触发器系统同步信号波形畸变严重、频率不断变化的特点,通过分析和比较各种滤波器的滤波效果,提出了一个多级数字滤波器联合滤波的方案。利用MATLAB软件搭建了该滤波器的仿真模型,并对其进行了仿真分析,理论上证明了该方案的可行性。通过估计算法的延时,证明了该数字滤波器满足实时信号处理的要求。     

Soliton control and bloch-wave filtering in periodic photonic lattices

We suggest a novel approach to soliton control and routing based on Bloch-wave filtering in periodic photonic structures. Taking a binary waveguide array as an example, we demonstrate that spatial solitons that belong to different spectral gaps can be selectively reflected from or transmitted through an engineered defect, which acts as a low- or high-pass filter for Bloch waves.     

The role of the envelope in processing iterated rippled noise.

Iterated rippled noise (IRN) is generated by a cascade of delay and add (the gain after the delay is 1.0) or delay and subtract (the gain is -1.0) operations. The delay and add/subtract operations impart a spectral ripple and a temporal regularity to the noise. The waveform fine structure is different in these two conditions, but the envelope can be extremely similar. Four experiments were used to determine conditions in which the processing of IRN stimuli might be mediated by the waveform fine structure or by the envelope. In experiments 1 and 3 listeners discriminated among three stimuli in a single-interval task: IRN stimuli generated with the delay and add operations (g = 1.0), IRN stimuli generated using the delay and subtract operations (g = -1.0), and a flat-spectrum noise stimulus. In experiment 2 the listeners were presented two IRN stimuli that differed in delay (4 vs 6 ms) and a flat-spectrum noise stimulus that was not an IRN stimulus. In experiments 1 and 2 both the envelope and waveform fine structure contained the spectral ripple and temporal regularity. In experiment 3 only the envelope had this spectral and temporal structure. In all experiments discrimination was determined as a function of high-pass filtering the stimuli, and listeners could discriminate between the two IRN stimuli up to frequency regions as high as 4000-6000 Hz. Listeners could discriminate the IRN stimuli from the flat-spectrum noise stimulus at even higher frequencies (as high as 8000 Hz), but these discriminations did not appear to depend on the pitch of the IRN stimuli. A control experiment (fourth experiment) suggests that IRN discriminations in high-frequency regions are probably not due entirely to low-frequency nonlinear distortion products. The results of the paper imply that pitch processing of IRN stimuli is based on the waveform fine structure.     

光电混合相关识别系统中匹配滤波器缩放比例的确定方法

在光电混合匹配滤波相关识别系统中,由于输入图像的频谱与匹配滤波器的形成方式不同,不能直接实现对应频率成份的准确对准。这个问题需要通过对匹配滤波器进行缩放来解决。根据透镜的傅里叶变换性质和计算全息理论,分别推导出输入图像的频谱的表达式和滤波空间光调制器加载了匹配滤波器后的透射函数的表达式,并根据这两个表达式得到匹配滤波器的缩放比例的公式,然后在实际的光学识别系统中对根据该公式计算的缩放比例进行了验证。实验结果表明,在该缩放比例下,相关峰的质量有较大改善,这说明此时输入图像的频谱与匹配滤波器对应频率成份实现了较好地对准。     

Perceived Pitch of Synthesized Voice with Alternate Cycles

Both in normal speech voice and in some types of pathological voice, adjacent vocal cycles may alternate in amplitude or period, or both. When this occurs, the determination of voice fundamental frequency (defined as number of vocal cycles per second) becomes difficult. The present study attempts to address this issue by investigating how human listeners perceive the pitch of alternate cycles. As stimuli, vowels /a/ and /i/ were synthesized with fundamental frequencies at 140 Hz and 220 Hz, and the effect of alternate cycles was simulated with both amplitude- and frequency-modulation of the glottal volume velocity waveform. Subjects were asked to judge the pitch of the modulated vowels in reference to vowels without modulation. The results showed that (a) perceived pitch became lower as the amount of modulation increased, and the effect seems to be more dramatic than would be predicted by existing hypotheses, (b) perceived pitch differed across vowels, fundamental frequencies, and modulation types, that is, amplitude versus frequency modulation, and (c) the prediction of perceived pitch was best made in the frequency domain in terms of subharmonic-to-harmonic ratio. These findings provide useful information on how we should assess the pitch of alternate cycles. They may also be helpful in developing more robust pitch determination algorithms.