一种适用于助听器的低失调自适应指向性算法

在噪声环境中助听器的性能会受到严重影响.但当噪声与期望信号处在不同方向时,在助听器中使用指向性传声器系统能够有效地抑制噪声,使助听器的使用者受益.本文基于自适应LMS(最小均方)算法提出了一种适用于助听器的低失调自适应指向性算法,用以动态调整传声器系统中滤波器的系数,使指向性模式的灵敏度最低点朝向噪声源方向,达到降噪的目的.相比于现有的LMS算法,本文引入了一种后验信噪比并将与其相关的信噪比补偿因子引入自适应步长的更新过程,有效改善了语音信号存在时的失调情况.最后,本文通过仿真验证了本文算法对失调的改善作用.     

基于最小误差熵的有源脉冲噪声控制算法

有源噪声控制(ANC)基于相消干涉的原理,能够有效降低低频噪声的影响。传统的ANC方法为滤波x最小均方(FxLMS)算法,该算法由于结构简单、易于实现,在实际中得到广泛应用。FxLMS假设环境中的噪声属于高斯噪声,但是许多实际环境中的噪声呈现脉冲噪声的特点。FxLMS方法利用二阶矩,但是在脉冲环境中由于误差的方差不存在,因此传统的FxLMS算法降噪性能下降,甚至造成系统的不稳定。最小误差熵(MEE)自适应滤波算法对脉冲信号鲁棒,将其应用到ANC系统,提出Fx MEE算法以应对环境中的脉冲噪声。仿真结果表明提出的方法在不同脉冲环境下相比于现有的算法均能实现较好的降噪性能。     

新型卡拉OK混响传声器

最近,市场推出了一种CDE—98A型卡拉OK混响传声器,它是一种新型的卡拉OK混响传声器(见图1)。该产品与普通传声器(如CDN—9型)相比,具有如下特点:①集传声与延时混响于一体的指向性     

基于FPGA自适应有源降噪耳机系统的设计

介绍了反馈式自适应有源降噪耳机系统的原理,设计并实现了基于ALTERA公司DE2开发板的FPGA自适应有源降噪耳机实时系统.系统中的自适应滤波器选择FIR滤波器结构,采用收敛速度较快且适合硬件实现的NLMS算法以满足音频信号实时性的要求.实验结果表明,采用FPGA实现自适应有源降噪耳机系统是有效的.     

两种抛物面形状的指向性传声器的比较

传声器系统指向性的实现主要有两种途径：一是通过特殊的声结构,二是通过传声器阵列。比较了一个带有抛物面形状反射面的传声器系统和与抛物面开口面积相同的圆形传声器阵列的差异。分别使用Kirchhoff-Helmholtz积分方程和阵列理论对这两种传声器系统的性能进行研究。数值模拟的结果表明,抛物面反射式传声器系统在高频时具有更高的灵敏度,其指向性通常也好于圆形传声器阵列。     

建筑施工有源振动噪声主动抑制系统设计

针对绿色建筑施工过程中的有源噪声问题,设计一种新的建筑施工有源振动噪声主动抑制系统,抑制建筑施工产生的高分贝噪声,避免影响当地居民生活、损害施工场地管理人员的听力。该系统通过传声器MIC1和MIC2采集建筑施工有源振动噪声信号后,采用LMS自适应滤波算法,去除噪声信号中干扰因子并通过数控放大器放大,将放大后的噪声信号传输至信号处理器中,先采用基于梯度下降的次级通道在线建模有源噪声控制方案,准确计算次级通道传递函数,再设定抑制噪声指令,叠加噪声控制信号与噪声信号,实现有源振动抑噪。经验证,某建筑施工场地降噪前噪声最大分贝高达79 dB,使用该系统后,噪声分贝数值降低到27～32 dB之间。实验不仅验证了该系统的有效性,还验证了系统具有较高的降噪量与降噪速度优势。     

利用DSP实现有源降噪功能的传声器设计

有源降噪传声器是一款利用高度集成的DSP/SOC(片上集成系统)语音处理器设计的语音降噪电声器件.该器件采用了语音环境噪声抑制技术,主要应用于移动电话、电话及电台手柄、头戴耳麦及免提耳麦等装置.利用双传声器信号接收方式,通过DSP语音处理器先进的语音清晰算法,可以有效识别动态环境噪音,从而在输出的正常语音中滤除上述的环境噪音,这样便可以保证通话的对方收听到清晰话音.     

WebRTC中一种基于DNN的噪声抑制算法的研究

WebRTC(Web Real-Time Communication)是谷歌开源的实时通信技术,包含了实现音视频会议系统所需的全部技术。文中对WebRTC的语音引擎中的降噪(Noise Suppression)算法进行了深入剖析,并且提出一种针对实际音视频会议系统环境下的基于DNN(Deep Neutral Network)的噪声抑制算法,实验结果表明提出的噪声抑制算法对于音视频会议系统中常见噪声有着很不错的噪声抑制效果,尤其对于人群嘈杂噪声。在低信噪比条件下的噪声抑制效果优于WebRTC中的降噪算法。     

改善宽带有源消声系统性能的间歇自适应IRLS算法

自适应有源消声控制器常用的算法是滤波-XLMS(FLMS)算法。该算法收敛速度慢,对噪声自相关矩阵特征值散布敏感,应用于宽带有源消声并不十分理想.本文基于最小二乘原理,提出间歇自适应IRLS算法作宽带噪声有源抵消.该算法利用声波从次级源传播到误差传声器的间隔内递推更新自适应滤波器权系数.IRLS算法的特点是收敛速度快,对噪声特征值散布不敏感.仿真结果表明:与采用FLMS算法的消声系统相比,采用IRLS算法的系统在收敛性,稳定性及降噪量等方面均有显著改进。文章最后分析了IRLS算法硬件实现的可行性。     

混响环境下基于卷积模型的欠定盲源分离

为了提高盲源分离(blind source separation, BSS)算法在混响和噪声环境下的鲁棒性,提出了一种适用于欠定情况下用于卷积混合信号的盲源分离算法。在该算法中,利用高混响环境下混合模型即使在时频(time-frequency, TF)域中仍具有卷积特性,并结合房间冲激响应(room impulse response, RIR)的统计规律,将时频域中的瞬时模型扩展到更适合高混响环境的卷积模型,进而构建一欠定盲源分离优化问题,最后,采用交替方向乘子法(alternating direction method of multipliers, ADMM)优化框架来求解该问题。仿真实验结果表明:在混响环境下,本文提出的基于卷积模型的盲源分离算法与现有盲源分离算法相比,具有非常明显的性能优势。      

可控指向性声柱

叙述了可控指向性声拄柱的产生背景与原因。即可用于高混响时间的空间,又不希望扬声器系统外形过大的地方。可控指向性声柱是利用电子计术、计算机技术、声学技术共同控制声柱的指向性。并且还可根据扩声房间声学特性进行调节。说明了如何通过延时、均衡、音量调节、相移调节等,使垂直平面波束变窄,指向角偏转,达到控制声柱指向性的目的。同时指出,可控指向性声柱,还可减少声反馈,提高扩声清晰度。     

基于改进小波域隐马尔可夫模型的遥感图像分割

该文提出了一种基于改进小波域隐马尔可夫树(HMT)模型进行图像分割的方法。该方法利用基于希尔伯特变换对的二维方向小波,这种小波变换具有平移不变性、方向检测性好的特点。同时该方法还利用拓展HMT对该改进小波域中尺度间的小波系数相关性进行建模,并结合多背景融合技术进行遥感图像的分割,得到了优于已有文献的分割结果,而且与同类算法相比,降低了算法所需的计算量。     

Artificial fish-swarm based coverage-enhancing algorithm for visible light sensor networks

An artificial fish-swarm based coverage-enhancing algorithm(AFCEA) for visible light sensor networks is proposed.In AFCEA,the improved optimization algorithm is used into the solution for coverage-enhancing in directional visible light sensor networks with the rotational direction model.Compared with other classic directional sensor networks coverageenhancing algorithms,AFCEA can achieve a higher directional sensor networks coverage with less iterative computing times.     

用双传声器模拟"8"字型指向性的一种方法

提出了运用两个全指向性传声器来模拟“8”字型指向性的一种测量方法。通过理论分析和实验验证。表明该方法可以准确地模拟“8”字型传声器的指向性特性，应用于室内音质参量的测试中。     

基于Ka/Ku相控阵天线的空基自组网协议设计

针对空基自组织网络的大容量通信需求,首先提出了基于频分复用的定向MAC协议,在邻居发现过程中将测距算法与多维尺度变换定位算法相结合得到每个节点的相对位置,并设计了双预约资源分配算法,完成定向数据传输;然后提出了定向路由协议,解决了次佳路由问题和路由应答风暴,并加入相邻搜索、链路质量评估和备用路由,降低了协议开销。空基自组网基于Ka/Ku相控阵天线的定向传播特性以及Ka/Ku频段频谱资源丰富的特点,使用频分复用、空分复用技术实现多个信道的高速并行传输,从而极大地提高网络的吞吐量。     

Genetic simulated annealing‐based coverage‐enhancing algorithm for multimedia directional sensor networks

Multimedia directional sensor network is one kind of directional sensing systems, whose coverage scheme is quite different from the omnidirectional sensing system. And it is often used in atrocious environmental surveillance, such as nuclear contaminative areas, where people can hardly arrive. In this paper, a genetic simulated annealing‐based coverage‐enhancing algorithm (GSACEA) is proposed as a coverage‐enhancing method in multimedia directional sensor networks. Firstly, GSACEA combines the genetic algorithm and simulated annealing algorithm into an algorithm with new architecture. Then, the proposed GSACEA is applied for the purpose of coverage‐enhancing in the case of directional sensor networks with rotational direction‐adjustable model. Finally, after series actions of genetic simulated annealing, the proposed method can find the approximate solution to the best area coverage rate. And according to the results of simulations, which compared the proposed method with several other classic coverage‐enhancing methods in directional sensor networks, it could be concluded that GSACEA can achieve the highest area coverage rate of directional sensor networks and reduce the iterative computing times simultaneously. Copyright © 2014 John Wiley & Sons, Ltd.     

A Learning Automata-Based Solution to the Priority-Based Target Coverage Problem in Directional Sensor Networks

In recent years, directional sensor networks composed of directional sensors have attracted a great deal of attention due to their extensive applications. The main difficulties associated with directional sensors are their limited battery power and restricted sensing angle. Moreover, each target may have a different coverage quality requirement that can make the problem even more complicated. Therefore, satisfying the coverage quality requirement of all the targets in a specific area and maximizing the network lifetime, known as priority-based target coverage problem, has remained a challenge. As sensors are often densely deployed, organizing the sensor directions into several cover sets and then activating these cover sets successively is a promising solution to this problem. In this paper, we propose a learning automata-based algorithm to organize the directional sensors into several cover sets in such a way that each cover set can satisfy coverage quality requirement of all the targets. In order to verify the performance of the proposed algorithm, several simulations were conducted. The obtained results showed that the proposed algorithm was successful in extending the network lifetime.     

Scheduling algorithms for extending directional sensor network lifetime

Recently, directional sensor networks that are composed of a large number of directional sensors have attracted a great deal of attention. The main issues associated with the directional sensors are limited battery power and restricted sensing angle. Therefore, monitoring all the targets in a given area and, at the same time, maximizing the network lifetime has remained a challenge. As sensors are often densely deployed, a promising approach to conserve the energy of directional sensors is developing efficient scheduling algorithms. These algorithms partition the sensor directions into multiple cover sets each of which is able to monitor all the targets. The problem of constructing the maximum number of cover sets has been modeled as the multiple directional cover sets (MDCS), which has been proved to be an NP-complete problem. In this study, we design two new scheduling algorithms, a greedy-based algorithm and a learning automata (LA)-based algorithm, in order to solve the MDCS problem. In order to evaluate the performance of the proposed algorithms, several experiments were conducted. The obtained results demonstrated the efficiency of both algorithms in terms of extending the network lifetime. Simulation results also revealed that the LA-based algorithm was more successful compared to the greedy-based one in terms of prolonging network lifetime.     

Optimal contention window size for IEEE 802.15.3c mmWave WPANs

The millimeter-wave (mmWave) band offers the potential for multi-gigabit indoor Wireless Personal Area Networks (WPANs). However, it has problems such as short communication coverage due to high propagation losses. In order to compensate for this drawback, utilization of directional antennas at the physical layer is highly recommended. In this paper, we consider the adequate contention window (CW) size for directional carrier sense multiple access with collision avoidance (CSMA/CA). To find the optimal CW size that enhances the performance of conventional directional CSMA/CA, we propose an enhanced directional CSMA/CA algorithm. The algorithm is considered in IEEE 802.15.3c, a standard for mmWave WPANs, under saturation environments. For the algorithm, we present a Markov chain model and analyze it for the no-ACK mode. The effects of directional antennas and the features of IEEE 802.15.3c Medium Access Control (MAC) such as backoff counter freezing are considered in the model. The optimal CW sizes for the two different objective functions are derived from the numerical results. The numerical results also show that the system throughput and average transmission delay of the proposed algorithm outperform those of conventional one and the overall analysis is verified by simulation. The obtained results provide the criterion for selecting the optimal parameters and developing a MAC protocol that enhances the performance of mmWave WPANs.     

DTRA: directional transmission and reception algorithms in WLANs with directional antennas for QoS support

Recent research results show that there are significant gains in throughput to be realized with directional transmission and directional reception compared to using omnidirectional; however, no specific reservation/scheduling algorithms are presented (Su Yi et al., 2003). In this article we propose a novel directional transmit and receive algorithm (DTRA) in wireless local area networks with directional antennas for quality of service support. To the best of our knowledge, all the previous work assumes omnidirectional reception at certain stages of the algorithms. However, the omnireceive requirement makes the protocol vulnerable to jamming. In this article no omniantennas or omnidirectional reception capability is assumed at all. The proposed algorithm exploits the beamforming capabilities of smart antennas to tailor resource access according to the services desired for individual traffic flows while limiting interference, probability of detection, and jamming in the network. Specifically, we present a TDMA-based MAC algorithm for load-dependent negotiation of slot reservations. Our new protocol offers four significant advantages: it assumes directional transmission/reception, it is distributed (i.e., it relies on local information only), it allocates slots to different links dynamically based on demand, and power control is easily carried out during neighbor discovery, reservation, and data transmission with very little overhead. We believe this is the first work on pure directional transmission and reception in wireless ad hoc networks. The algorithm can be used in many commercial and military applications. Preliminary simulation results indicate that DTRA performs much better than IEEE 802.11 for the network considered.