独创性声明
本人声明所呈交的学位论文是本人在导师指导下进行的研究工作及取得的研究成果。据我所知，除了文中特别加以标注和致谢的地方外，论文中不包含其他人已经发表或撰写过的研究成果，也不包含为获得电子科技大学或其它教育机构的学位或证书而使用过的材料。与我一同工作的同志对本研究所做的任何贡献均已在论文中作了明确的说明并表示谢意。 作者签名：日期：年月日
论文使用授权
温泉浴片本学位论文作者完全了解电子科技大学有关保留、使用学位论文的规定，有权保留并向国家有关部门或机构送交论文的复印件和磁盘，允许论文被查阅和借阅。本人授权电子科技大学可以将学位论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存、汇编学位论文。
（保密的学位论文在解密后应遵守此规定）
作者签名：导师签名：
日期：年月
摘要
摘要
声反馈是出现在剧院、多媒体教室、会议室等公共扩声系统中的常见问题，它经常使音频扩声系统的性能发生显著衰退，极端情况下会使得系统变得不稳定，发生啸叫。抑制声反馈是扩声系统亟待解决的问题。从改善房间声学环境入手或在扩声器中加入均衡器的传统方法通常操作不便，并且费用较高。相位调制法和增益降低法是比较灵活的啸叫抑制方法，但是在实时性、扩声增益提高以及音质损失之间很难获得很好的平衡，且多为在啸叫发生后进行检测和处理，影响用户的主观听觉感受。 自适应啸叫抑制法克服了相位调制法和增益降低法的缺点，能够实现实时处理，同时大幅提高系统增益，带来较小的声音失真，而且硬件成本较低。本论文以自适应啸叫抑制法为主要研究对象，在深入分析自适应算法理论的基础上，对自适应啸叫抑制算法和去相关技术进行了讨论和研究。论文首先介绍了自适应滤波器基本原理，并重点研究了LMS、NLMS、VMLMS以及VSNLMS算法。随后研究了消除信号相关性的去相关技术，包括噪声注入法、插入延时法、时变处理法和非线性处理法。接着阐述了利用自适应线性预测进行啸叫抑制的原理。由于现阶段对啸叫抑制系统还没有统一的测评标准，本文从系统性能、放大能力、音质失真三方面采用多种评价标准结合的方法对啸叫抑制进行评价。 为了便于模拟啸叫发生的声场环境，论文搭建了MATLAB啸叫抑制仿真平台，并在此仿真平台中对基
于自适应线性预测的自适应啸叫抑制算法及去相关技术进行仿真和分析实验结果。考虑到计算复杂度、扩声增益和音质失真等因素，论文选择了NLMS算法和VMLMS算法进行DSP实现。硬件平台选择以TI公司的定点数DSP芯片(TMS320DM6437)为核心的EVM板，论文分别验证了DSP算法在模拟声场和真实声场中的啸叫抑制性能。为实现DSP与MATLAB仿真平台的实时连接，本文设计了DSP与MATLAB的通信机制。经过大量仿真测试和实际声场测试，验证了本文的啸叫抑制方案能够对信号实时处理，啸叫抑制效果较好，并且能获得良好的声音质量。
关键词：啸叫抑制，自适应算法，去相关技术，仿真平台，DSP实现
I
ABSTRACT
The acoustic feedback problems exist in the theatres, multimedia classrooms, conference rooms and other public addressing systems. It often causes significant performance degradations in sound reinforcement system; in the worst case, the systems become unstable and howling occurs. Therefore, acoustic feedback is a big issue that needs solving in sound reinforcement system.Traditional methods of howling suppression, such as improving rooms’ acoustic property or cascading equalizers in the public addressing system, are inconvenient to operate, enhance the syst
em gain only a little and damage the fidelity of acoustic signal.Phase-Modulation Methods and Gain Reduction Methods are flexible, but difficult to get good balance among real-time processing, system gain and the fidelity of acoustic signal. Moreover, FSM always detect and process howlingafter occurring, which makes the users uncomfortable.
Acoustic feedback suppression(AHS) overcomes other methods’shortcomings, does little harm to speech signals, improves the systems'gain prominently and is easy to operate.The thesis focuses on AHS. Based on in-depth analysis on the theory of adaptive algorithm, the adaptive howling suppression algorithmsand the decorrelation techniquesare discussed. Firstly, the thesis introduces the basic principle of adaptive filter and LMS/NLMS/VMLMS/VSNLMS algorithms. Then, to avoid a biased and slowly converging feedback estimation, the thesis gives an introduction of four kinds decorrelation techniques, including Noise injection, Inserting delay, Half-wave rectification and Frequency shifting. After that, the thesis studies adaptive linear prediction for real-time application. Although AHS algorithms have become common in public addressing systems, there is no standardized objective procedure available for evaluating them. The thesis discusses objective measures for evaluating AHS algorithms from the system performance, the maximum stable gain and the sound quality.
In order to provide a virtual environment for the simulation of AHS, the thesis proposes a MATLAB platformand introduces the simulation of AHS. Based on the evaluation criteria of simulation results, the thesis adopts NLMS and VMLMS adaptive howling suppression algorithm, designing the AHS schemausing the fixed DSP chip (TMS320DM6437) of TI and other relevant peripheral equipment. Not only does the
II
AHS schema implement in a virtual sound reinforcement system, but also in a real system. The tests shows that the AHS schema being implemented on DSP can suppress the howling well in the meantime get better performance in evaluation.
Keywords: howling suppression, adaptivealgorithms, decorrelation methods, simulation platform, DSP’s implementation
III
目录
目录
高温气化炉热电偶第一章绪论 (1)
1.1声反馈现象简介 (1)
1.2啸叫抑制技术的研究现状 (3)
1.2.1相位改变法 (3)
1.2.2增益降低法 (3)
1.2.3自适应啸叫抑制法 (4)
1.3啸叫抑制评价体系研究现状 (5)
1.4论文的研究内容与结构安排 (5)
第二章自适应啸叫抑制算法原理及评价标准 (7)
2.1自适应滤波器的基本概念 (7)
橡胶软化油2.2自适应滤波算法 (9)
2.2.1 LMS算法 (9)
2.2.2 NLMS算法 (11)
2.2.3 VMLMS算法 (12)
2.2.4 VSNLMS算法 (12)
2.3自适应啸叫抑制法的去相关技术 (13)
2.4自适应线性预测啸叫抑制原理 (14)
2.5啸叫抑制评价标准 (16)
2.5.1基于系统性能的评价标准 (16)火漆印章头如何自制
医用消毒灭菌2.5.2基于放大能力的评价标准 (17)
2.5.3基于音质的评价标准 (17)
2.6本章小结 (20)
电机风罩
第三章自适应啸叫抑制算法仿真实验研究 (21)
3.1MATLAB啸叫抑制仿真平台 (21)
3.1.1房间冲激响应模块 (22)
3.1.2 扩声器冲激响应模块 (24)
3.2算法仿真与结果分析 (25)
3.2.1 啸叫的产生与实验参数的选择 (25)
3.2.1.1啸叫的产生 (25)
3.2.1.2自适应滤波器阶数的选择 (26)
IV
豫公网安备41160202000603
站长QQ:729038198
关于我们
投诉建议