Speech Intelligibility in a Background Noise and Noise-induced Hearing Loss

A significant improvement in speech intelligibility in a background noise was shown in a group of industrial subjects conditioned to working in noise compared with a control group of university staff. Progressive deterioration of speech intelligibility in noise was found with noise-induced hearing loss after losses had occurred at the 2 kHz pure-tone audiometric frequency.     

基于G.729的网络丢包自适应语音编码器

文章分析了错误隐藏技术在不同的网络丢包情况下的性能以及不同参数的敏感程度,提出了一种非对称网络丢包错误保护技术,并与G．729语音编码器相结合,提出了一种固定码率12．0kbps的网络自适应语音编码器。实验表明其具有良好的效果。     

Short- and Long-Term Packet Loss Behavior: Towards Speech Quality Prediction for Arbitrary Loss Distributions

A speech-quality-oriented classification of packet loss distributions is proposed according to both the short- and long-term loss behavior. While the short-term behavior (microscopic loss behavior) relates to the effect of packet loss on the coder and packet loss concealment performance, the long-term loss behavior (macroscopic loss behavior) is defined so that it reflects the loss behavior that ultimately leads to speech quality that perceptively changes over time. Based on this classification, different parametric (objective) modeling approaches for predicting speech quality are discussed. To this aim, a packet loss averaging approach is presented for modeling speech quality under short-term loss. Starting from this model, two different ways for predicting speech quality under long-term-dependent packet loss are analyzed and compared to auditory (subjective) test results: quality prediction based on the averaging at packet trace level as provided, e.g., by the E-model , and the prediction based on the time-averaging of estimated instantaneous quality profiles, as suggested, e.g., by . From this comparison, the suitability of the different approaches for network planning are discussed, and their limitations in case of particular loss distributions are pointed out.     

Subjective Quality of Speech Over Packet Networks as a Function of Packet Loss, Delay and Delay Variation

An expanding proportion of voice traffic is being carried by packet networks. Speech quality can be impaired in qualitatively new ways in packet networks when packets are lost or the spacing between them is distorted. Three parameters that characterize the performance of packet networks were examined for their relative impact on speech quality as judged by human observers: network delay or latency, packet loss, and packet delay variation or jitter. We manipulated these variables via a network emulator made available by NIST. This report summarizes five laboratory experiments that examined the variables in a variety of experimental procedures for presenting and judging speech. The experiments agreed in showing that the relative importance of the variables for affecting speech quality was, in decreasing order: packet loss, jitter, delay. The effect on speech quality of 200 ms of network delay was shown to be equivalent to the effect of one percentage point of packet loss. Many consumers also traded off some speech quality for a free, added feature, unified messaging.     

噪声环境下统计分类语音检测的自适应算法

可靠的语音检测算法是稳健语音识别系统所必需的。该文针对统计分类语音算法对训练数据的依赖问题,提出自适应算法在线动态更新分类模型。实验结果表明在训练和识别环境失配情况下,自适应算法可以明显提高语音检测的稳健性。在稳态的噪声环境下,语音检测的正确率有3%-10%的提高;在时变的噪声环境下,语音检测的正确率有7%-28%的提高。     

Internet中的包延迟分布与包丢失关系研究

包延迟的分布特征是Internet端到端行为特征的一个重要组成部分,前人已在该方面进行了大量研究,但许多研究结论只适用于丢包率较小的情况,通过研究我国科技网和教育网上34条端到端路径上的延迟特征,得出了如下结论：（1）包延迟的分布特征与丢包率存在一定的关系;（2）在丢包率较小的情况下,包延迟的分布多具有单峰性,但随着丢包率的增大,包延迟的分布不再具有单峰性,而是呈现出越来越分散的特点;（3）随着丢包率的增大,固有延迟的发生次数呈现逐渐减少的趋势,当丢包率增大到一定程度,固有延迟的发生次数就很少了。     

网络控制中的丢包问题分析

介绍在网络控制（NCS）中出现丢包问题时的一种解决方法,所用的控制对象为应用广泛的三箱系统。通过实验模拟网络丢包的发生．收集到大量数据对网络状态进行分析．并通过仿真得到网络对控制对象的影响。     

Image Deblurring in the Presence of Impulsive Noise

Consider the problem of image deblurring in the presence of impulsive noise. Standard image deconvolution methods rely on the Gaussian noise model and do not perform well with impulsive noise. The main challenge is to deblur the image, recover its discontinuities and at the same time remove the impulse noise. Median-based approaches are inadequate, because at high noise levels they induce nonlinear distortion that hampers the deblurring process. Distinguishing outliers from edge elements is difficult in current gradient-based edge-preserving restoration methods. The suggested approach integrates and extends the robust statistics, line process (half quadratic) and anisotropic diffusion points of view. We present a unified variational approach to image deblurring and impulse noise removal. The objective functional consists of a fidelity term and a regularizer. Data fidelity is quantified using the robust modified L ¹ norm, and elements from the Mumford-Shah functional are used for regularization. We show that the Mumford-Shah regularizer can be viewed as an extended line process. It reflects spatial organization properties of the image edges, that do not appear in the common line process or anisotropic diffusion. This allows to distinguish outliers from edges and leads to superior experimental results.     

关于语音数字综合业务网中语音包长的进一步探讨

利用汉语语音的统计特性,对文献[3]中提出的语音包化协议进行了改进,在理论上证明了最佳语音包长的存在并给出了最佳语音包长所必须满足的数学表达式。     

基于正交小波包分解的语音去噪增强

对带噪语音信号进行增强,是语音信号处理中一个重要的研究课题.由于噪声影响语音质量,这抑制背景噪声,利用小波包良好的时频分析能力,能较好模拟人耳基底膜频率分析特性的特点,提出基于正交小波包的语音去噪增强算法,算法首先把含噪语音信号分解于不同的频率范围内,根据"3σ规则",确定不同频率下的阈值,并采用动态阈值法对各层进行阈值处理,最后对处理后的语音信号反变换得到增强后的信号.在MATLAB平台上,对带噪语音信号去噪增强,实验结果表明,方法在抑制白噪声的同时减小了语音信息的损失,输出语音在保证可懂度的同时达到了较好的输出语音效果.     

选择传递攻击中的异常丢包检测

该文提出了一种基于检查点的多跳确认方案来检测选择传递攻击所导致的异常丢包．在这个方案中，能够随机地选取传递路径中的部分节点为检查点，负责包的确认．这种随机检查点选择技术能够避免部分节点成为敌方俘获的目标，从而在保证检测能力的同时有效地提高了系统的健壮性．文章对检测率进行了理论分析，并进一步通过模拟实验对检测率进行了验证．     

无线网络丢包检测技术的研究

相较于有线网络,无线网络具有误码率高、时延大、带宽低等特性。因此,考虑到TCP直接应用于无线环境的局限性,这方面的研究者们提出了多种TCP拥塞控制的改进机制,这些方案一般没有考虑误码丢包对数据发送速率的影响。本文详细的讨论了有关无线网络丢包检测的各种实施策略,并介绍了若干丢包检测技术的实现原理。     

无线网络丢包检测技术的研究

相较于有线网络,无线网络具有误码率高、时延大、带宽低等特性.因此,考虑到TCP直接应用于无线环境的局限性,这方面的研究者们提出了多种TCP拥塞控制的改进机制,这些方案一般没有考虑误码丢包对数据发送速率的影响.本文详细的讨论了有关无线网络丢包检测的各种实施策略,并介绍了若干丢包检测技术的实现原理.     

Reducing the Effects of Noise in Image Reconstruction

Fourier spectral methods have proven to be powerful tools that are frequently employed in image reconstruction. However, since images can be typically viewed as piecewise smooth functions, the Gibbs phenomenon often hinders accurate reconstruction. Recently, numerical edge detection and reconstruction methods have been developed that effectively reduce the Gibbs oscillations while maintaining high resolution accuracy at the edges. While the Gibbs phenomenon is a standard obstacle for the recovery of all piecewise smooth functions, in many image reconstruction problems there is the additional impediment of random noise existing within the spectral data. This paper addresses the issue of noise in image reconstruction and its effects on the ability to locate the edges and recover the image. The resulting numerical method not only recovers piecewise smooth functions with very high accuracy, but it is also robust in the presence of noise.     

MPLS故障恢复中的丢包与失序研究

该文分析了MPLS网络中的Makam和Haskin两种故障恢复机制,Makam机制会造成的数据包的丢失,Haskin可以避免这个问题,但会导致数据包失序的问题,该文提出了在Haskin的基础上使用缓冲区来避免数据包的失序,并给出了缓冲区大小的估计式,以及估计式中相关参数的近似计算方法.     

噪声环境下的语音识别性能研究

在变强噪音的情况下,语音识别的正确率会迅速下降;当噪声较强并且强度不断发生变化的时候,端点检测是一个难题;提出了两种方法保证噪声较强而且强度不断发生改变情况下的语音识别率：基于LPC距离的端点检测算法和白适应的抗噪语音特征参数提取算法;经过实验证明,采用了这两种不同于传统算法的新方法后,变强噪音情况下的语音识别率得到了明显的改善。     

Simulation and Analysis of Packet Loss in User Datagram Protocol Transfers

Understanding packet loss patterns in Internet Protocol (IP) networks is important for achieving the desired quality of service in multimedia transfers. In this paper, we study the loss patterns in video transfers using User Datagram Protocol (UDP) in a congested packet network. We use trace-driven ns-2 simulations to collect packet loss traces in networks, and we apply wavelet analysis to investigate the behavior of packet loss on various time-scales. We show that time-scales are essential for understanding loss behavior and that packet loss exhibits long-range dependence over the coarser time-scales.     

一种高噪声环境下语音检测算法的仿真与应用

该文提出了一种高噪声环境下的自适应语音检测新算法。该算法利用了语音短时能量及帧内短时自相关的特性,两个自适应判决门限根据期望的误判率调整,无需事先给出噪声统计信息,适用于平稳噪声、缓变的非平稳噪声及脉冲噪声的情况,且可以实时实现。     

网络丢包现象原因初探

网络丢包现象时有发生,通常用ping命令来检测丢包率情况。网络丢包主要集中在线路故障、设备故障、网络拥塞、路由错误等方面,并探讨了其原因。丢包的原因非常多,但难以用系统的方法进行排查,应根据具体的情况进行分析。     

NBFI系统的稳定性分析

NBFI（基于网络的反馈连接）是一类基于网络反馈连接的系统。文中研究了此模型的数据包丢失的问题,将带有有界任意丢包问题的NBFI系统建模成一般的线性切换系统．并应用切换Lyapunov函数方法加以分析,进而给出了NBFI系统渐近稳定的充分条件．并将结果推广到单位时延的情况。最后给出仿真,从而验证了结论的正确性。