Optimal design of loudspeaker arrays for robust cross-talk cancellation using the Taguchi method and the genetic algorithm

An optimal design technique of loudspeaker arrays for cross-talk cancellation with application in three-dimensional audio is presented. An array focusing scheme is presented on the basis of the inverse propagation that relates the transducers to a set of chosen control points. Tikhonov regularization is employed in designing the inverse cancellation filters. An extensive analysis is conducted to explore the cancellation performance and robustness issues. To best compromise the performance and robustness of the cross-talk cancellation system, optimal configurations are obtained with the aid of the Taguchi method and the genetic algorithm (GA). The proposed systems are further justified by physical as well as subjective experiments. The results reveal that large number of loudspeakers, closely spaced configuration, and optimal control point design all contribute to the robustness of cross-talk cancellation systems (CCS) against head misalignment.     

Comparative study of audio spatializers for dual-loudspeaker mobile phones

MPEG-1, layer 3 handsets equipped with dual loudspeakers and three-dimensional audio modules have received much attention in the market of consumer electronics. To create spatial impression during audio reproduction, the head-related transfer function (HRTF) and the crosstalk cancellation system (CCS) are key elements in many audio spatializers. However, there are many factors that one should take into account during the design and implementation stages of an audio spatializer in the handset application. In the paper, a comprehensive study was undertaken to compare various audio spatializers for use with dual-loudspeaker handsets, in the context of inverse filtering strategies. Two deconvolution approaches, the frequency-domain method and the time-domain method, are employed to design the required inverse filters. Different approaches to design audio spatializers with the HRTF, CCS, and their combination are compared. In particular, two modified CCS approaches are suggested. Issues in the implementation phase such as regularization, complex smoothing, and structures of inverse filters are also addressed in the paper. Comprehensive objective and subjective tests were conducted to investigate the aforementioned aspects of audio spatializers. The data obtained from the subjective tests are processed by using the multianalysis of variance to justify statistical significance of the results.     

激光辐照TDI-CCD相机饱和串扰效应及侧斑建模仿真分析

根据推扫式线阵TDI-CCD成像系统的信号存储、传输与转换原理,分析了其在激光作用下产生不同饱和串扰现象的机理,建立了激光辐照TDI-CCD红外相机饱和串扰效应模型;考虑了视场外激光干扰过程中出现的侧斑现象,同时借助光学追迹模型,实现了连续激光干扰星载红外相机的成像仿真过程;通过图像质量评估因子定量分析了不同入射条件下激光辐射对相机输出图像质量的影响。结果表明:入射角不同,激光成像结果不同.选用1.064μm视场外激光在一定入射条件下,当改变激光入射角从2.86°到2.89°时,激光将出现侧斑;当激光功率密度提高1~4倍,光斑干扰面积百分比将不同程度的扩大.     

Sound localization of stereo reproduction with parametric loudspeakers

A parametric loudspeaker radiates an audible signal by the interaction of the primary wave that is amplitude modulated and is known as a super-directivity loudspeaker. The parametric loudspeaker is one of the prominent applications of nonlinear acoustics. So far, the applications have been limited monaural reproduction sound system for public address in museum, station, street etc. In this paper, we investigated sound localization of stereo reproduction using two parametric loudspeakers in comparison with that using two ordinary dynamic loudspeakers. In subjective tests, the binaural information ILD (Interaural Level Difference) or ITD (Interaural Time Delay) was focused on. To investigate the characteristics of sound localization in a wide listening area, three typical listening positions were picked up. Signals were 500 Hz, 1 kHz, 2 kHz and 4 kHz pure tones and pink noise. The used parametric loudspeaker was an equilateral hexagon. The subjective test led to the results that when the parametric loudspeakers were used, the listeners at the three typical listening positions perceived the correct sound localization of not only pure tone but also pink noise and when the ordinary dynamic loudspeakers were used, except for the case of pure tone with ITD, the tendency was almost similar to those using the parametric loudspeakers. The second subjective tests were conducted in order to investigate in details the difference between parametric loudspeakers and ordinary dynamic loudspeakers by increasing the number of subjects. In the case of ITD and 500 Hz using the ordinary dynamic loudspeakers, three types of sound localization were categorized, in which the reversed type was major and the normal and the other types were minor. The ILDs which were measured with a dummy head and were calculated with several formulas were almost the same and indicated the reasons of the reversed typed sound localization and a serious influence of the crosstalk. It was found that in the case of pure tone with ITD, the contradiction between the binaural information ILD and ITD is remarkable, because the directivity of the ordinary dynamic loudspeakers was so dull that the crosstalk components had a serious influence on sound localization. It was determined the parametric loudspeaker could transmit correct binaural information to the listener, because the directivity of the parametric loudspeakers was so sharp that it suppressed the cross talk components.     

骨导振子佩戴位置对重放声的影响*

骨导振子佩戴位置会影响骨传导声重放的性能,但已有研究还不够全面和完善。针对11名双耳听力正常的受试者,采取不同的骨导振子佩戴位置,对骨传导声重放在听力阈值、主观音质评价和语言清晰度3个方面进行了研究。实验结果表明不同的佩戴位置会影响骨传导声重放性能,髁骨位置在3个实验都表现最好,髁骨的听力阈值比乳突位置平均低8.7 dB,主观音质评价得分平均高乳突38.4分。该文的研究可为骨导振子佩戴位置的选择提供依据,并为声重放质量的改进提供参考。     

利用自相关函数和双耳自相关函数分析对交通噪声特征参量的提取~

对实地双通道测量获得的道路交通噪声和铁路噪声信号样本进行了自相关函数和双耳自相关函数(Interaural CrossCorrelation Function)的分析。进而通过对噪声样本时间因子和空间因子的相关性分析、主成分分析和主观评价实验,得到了3个铁路噪声源特征参量物理因子和4个道路交通噪声源特征参量物理因子。发现与传统的声压级测量相比,表征声音信号时间特性和空间特性的这7个物理量可以更全面、准确地表征交通噪声的特性。在对道路噪声进行测量或分析时,掌握与声源视觉宽度和音调感相对应的物理因子以及双耳时延和初始能量,就可获悉与人的主观评价相一致的道路交通噪声特征信息;对铁路噪声而言,掌握与声源视觉宽度相对应的物理因子以及双耳时延和声音的重复性特征,就可以得到与入主观评价相一致的铁路噪声特征信息。综合道路噪声特征参量和铁路噪声特征参量可以发现,双耳时延和与声源视觉宽度相对应的物理因子是与人的主观反应最为一致的主成分指标,说明噪声中决定人的评价的最主要的因素是代表空间特征的信号因子。      

Directional cancellation of acoustic noise for home window applications

This paper focuses on an active noise cancellation system for a home window using a transparent acoustic transducer. In a traditional active noise cancellation system, direct microphone measurements are used for reference and error signals. In the case of the window application, both external and internal sound would be picked up by such microphones. This leads to adverse effects on the performance of the active noise cancellation system and also to distortion of the internal sound. To address this problem, a wave separation technique is proposed to separate the internal and external components of sound. The wave separation algorithm is based on the use of two microphones and an algorithm that separates components based on their direction of travel. An active noise cancellation system is implemented using wave separation for both the error and reference signal measurements. The performance of the resulting ANC system is experimentally tested in a cabin equipped with a window and results are presented. Experimental results show that the new system is able to accurately preserve desired internal sound while cancelling uncorrelated external noise.     

眼镜式立体显示中的串扰分析及消除方法研究

随着立体显示技术的广泛应用,立体显示图像质量受到了越来越多的重视。目前,串扰现象是影响立体显示技术中图像质量和观看舒适度最主要的因素之一。为消除眼镜式立体显示技术中的串扰现象,提出了一种基于图像处理的串扰消除方法。该方法从观看者的角度出发,将观看通道与非观看通道具有相同灰度时透过观看通道眼镜测得的亮度定义为理想输出亮度,利用亮度计测量得到的眼镜式立体显示器的光输出特性,经过计算得到左右视图灰度查找表,应用左右视图灰度查找表在显示立体图像时消除串扰。分析结果表明,提出的方法平均串扰减少率的理论值高达75%。同时,提出的方法合理利用了非观看通道的漏光等串扰信号,将立体图像亮度提高了12%。提出的方法应用简单,同时适用于时间复用和空间复用的眼镜式立体显示技术。     

Energy-dependent cancellation of diffraction spots due to surface roughening

The low-energy electron diffraction (LEED) pattern of the step-kinked Pt{531} surface at 200 K shows energy-dependent cancellation of diffraction spots over unusually large energy ranges, up to 100 eV. This cannot be reproduced theoretically when a flat surface geometry is assumed. A relatively simple model of roughening, however, involving 0.25 ML of vacancies and adatoms leads to very good agreement with the experiment. The cancellation of intensities within a very narrow range of adatom or vacancy coverages is caused by the interference of electrons emerging from different heights but similar local environments. This is a rare example where the energy dependence of integrated LEED spot intensities is dramatically affected by the long-range arrangement of atoms.     

120 W的二极管泵浦Nd:YAG绿光激光器

对激光二极管泵浦的NdYAG声光调Q腔内倍频固体激光器的折叠腔型进行了研究,当泵浦功率达800 W时,在V型腔上实现了脉宽为80 ns、重复频率为10 kHz、发散角为6 mrad、绿光功率为112 W的输出;在Z型腔上实现了脉宽为95 ns、重复频率为10 kHz、发散角为4 mrad、绿光功率为120 W的输出.比较两种腔型的实验结果可看出,Z型腔由于插入的光学元件较多,腔长较长,输出激光的脉宽较宽,但输出激光的光束质量有明显的提高.     

The flavour of natural SUSY

We study the screening effect for the multiparton interactions (MPI) for proton–deuteron collisions in the kinematics where one parton belonging to the deuteron has small \(x_1\) , so the leading twist shadowing is present, while the second parton ( \(x_2\) ) is involved in the interaction in the kinematics where shadowing effects are small. We find that the ratio of the shadowing and the impulse approximation terms is approximately a factor of 2 larger for MPI than for the single parton distributions. We also calculate the double parton antishadowing (DPA) contribution to the cross section due to the independent interactions of the partons of the projectile proton with two nucleons of the deuteron and find that shadowing leads to a strong reduction of the DPA effect. For example, for the resolution scale \(Q_1^2 \sim 4\)   \(\text{ GeV }^2\) of the interaction with parton \(x_1\) we find that shadowing reduces the DPA effect by \(\sim \) 30 %. It is argued that in the discussed kinematics the contribution of the interference diagrams, which correspond to the interchange of partons between the proton and neutron, constitutes only a small correction to the shadowing contributions.     

Room reverberation effects in hearing aid feedback cancellation

Room reverberation can affect feedback cancellation in hearing aids, with the strength of the effects depending on the acoustical conditions. These effects were studied using a behind the ear (BTE) hearing aid mounted on a dummy head and coupled to the ear canal via an open fitting. The hearing aid impulse response was measured for the dummy head placed at eight closely spaced locations in a typical office. The feedback cancellation in the hearing aid used a set of filter coefficients that were initialized for one location within the room, and then allowed to adapt to the feedback path measured at the same or to a different location. The maximum stable gain for the hearing aid was then estimated without feedback cancellation, for the initial set of feedback cancellation filter coefficients prior to adaptation, and for the feedback cancellation filter after adaptation. A low-order ARMA model combining a fixed set of poles with an adaptive FIR filter is shown to be effective in representing the feedback path exclusive of reverberation. Increasing the adaptive filter length has only a small benefit in improving the feedback cancellation performance due to the inability of the system to model the room reverberation. The mismatch between the modeled and actual feedback paths limits the headroom increase that can be achieved when using feedback cancellation, and varies with the location within the room.     

含遮蔽抛射沉积模型的有限尺寸效应

含遮蔽抛射沉积模型是在抛射沉积(BD)模型的基础上考虑了粒子以一定的角度分布倾斜入射的情况.本文应用外推方法确定了大尺寸极限下含遮蔽抛射沉积模型的各标度指数,讨论了该模型的有限尺寸效应及其标度性质.从模拟结果可以看出含遮蔽BD模型的有限尺寸效应与BD模型有所不同,遮蔽这种非局域作用可以显著地改变BD模型的标度性质. 关键词： 遮蔽效应 抛射沉积模型 有限尺寸效应 动力学标度     

傅里叶变换光谱仪多次反射杂光对调制度的影响分析

为满足遥感探测领域对高光谱干涉探测仪的高信噪比和高光谱分辨率的要求,针对我国目前在研高光谱分辨率傅里叶变换光谱仪,详细分析了采用分束器及补偿器分光方案的迈克尔逊干涉仪中,增透面上多次反射杂光对光谱仪调制度的影响。分析表明增透面透过率越低,光谱仪调制度越低。理论分析发现,引入分束器和补偿器的楔角和倾斜角可以实现正常光斑与多次反射光斑分离,从而减弱甚至消除多次反射杂光的影响。通过理论计算给出了二次反射杂光与正常光路夹角与楔角和倾斜角的关系式,并依据光斑分离要求确定了楔角和倾斜角优化方法。由于干涉仪结构参数的相互关联特性,在优化楔角和倾斜角后,需要对入射角进行调整,使得反射光路与透射光路关于分束面对称,以消除其对光谱分辨率的影响;需要对补偿器厚度进行调整匹配,消除由于角度调整引入的正常光路光程差改变导致的调制度下降。按此步骤进行设计优化,在保持原有高精度设计指标的前提下,可消除干涉仪多次反射杂光的影响,该干涉仪优化设计步骤及结构参数调整方法适用于采用分束器补偿器分光方案的傅里叶变换光谱仪。     

基于复用体全息光栅的光学相控阵放大级串扰优化

提高各通道输出光信噪比,进行了复用体全息光栅的优化设计研究。推导了适用于角度放大器的多路复用体光栅耦合波理论,并与单路耦合波理论进行了比较。针对复用体光栅中的串扰问题,研究了调整光栅结构参数优化串扰的规律,并进行了实验验证。研究结果表明:当相邻两路体光栅的布拉格角间隔小于二者角度选择半宽之和时,相互间串扰较强,必须使用多路耦合波理论描述复用体光栅中波的衍射行为。调整相邻路体光栅的矢量倾斜角间隔、减小光栅周期和增加光栅厚度都可以降低串扰,其中调整矢量倾斜角和光栅周期优化效果明显但会降低角放大率,增加介质厚度不影响角放大率但需要厚度增加数倍才有效。     

Subjective and objective verifications of the inverse functions of binaural room impulse responses

The binaural room impulse responses (BRIRs) can be applied to 3-D sound field reconstruction, virtual reality, noise control, et al. Because the BRIRs are non-minimum phase functions, it is difficult to find the exact inverse functions of the BRIRs, especially when there are two or more sources in a reverberant space. In this work, a method was proposed to find the inverse functions of BRIRs with two sound sources in a reverberant space. The concept of time delays and the method of weighted least squares were used to find the causal, however, approximate inverse functions. The accuracy of the inverse functions was first evaluated objectively by a dummy head system. The result shows that the distortion due to crosstalk and room reverberation can be improved by 16∼18 dB. The inverse functions were also verified subjectively by 20 students. The result of subjective evaluation also shows that the inverse functions can be used successfully to reduce the crosstalk effect and the room reverberation.     

Influence of measurement methodology of head-related transfer functions on auditory perception

Head-related transfer functions(HRTFs) are the core of virtual auditory display and relevant applications. However,a standard method for HRTF measurements has not been established. This work examines the influence of different HRTF measurement methodologies on auditory perception. First, the diffusion-field equalization was proposed and applied to HRTFs of a single dummy head(KEMAR) from five different datasets. Then,the spectral deviations among the HRTFs were calculated and analyzed. Finally, a series of subjective listening experiments(including localization and discrimination experiments) were conducted. Results indicate the diffusion-field equalization is an effective pre-processing method which reduces the difference in HRTF magnitude spectra caused by different measurement methodologies. Moreover,the HRTFs from different measurement methodologies have similar localization performance below 12 kHz, whereas the inter-dataset differences in timbre are distinct leading to audible discrimination.     

Listening difficulty as a subjective measure for evaluation of speech transmission performance in public spaces

Listening difficulty ratings, using words with high word familiarity, are proposed as a new subjective measure for the evaluation of speech transmission in public spaces to provide realistic and objective results. Two listening tests were performed to examine their validity, compared with intelligibility scores. The tests included a reverberant signal and noise as detrimental sounds. The subject was asked to repeat each word and simultaneously to rate the listening difficulty into one of four categories: (1) not difficult, (2) a little difficult, (3) fairly difficult, and (4) extremely difficult. After the tests, the four categories were reclassified into, not difficult [response (1)] and some level of difficulty, (the other 3 responses). Listening difficulty is defined as the percentage of the total number of responses indicating some level of difficulty [i.e. not (1)]. The results of two listening tests demonstrated that listening difficulty ratings can evaluate speech transmission performance more accurately and sensitively than intelligibility scores for sound fields with higher speech transmission performance.