声反馈研究.doc

声反馈研究

摘要

声反馈是指音频信号的一部分与输入信号同相位地加到输入端，导致幅度不断增大而引起某些频率的震荡。由声反馈引起的啸叫不仅破坏了整个音响系统的正常工作状态，而且让演员或讲话者颇感烦躁，让观众和听众扫兴，更让音响设备的操作员十分尴尬。因此，了解声反馈并及时找到较好的办法来避免或尽量减少声反馈引起的啸叫是非常关键的，具有很重要的现实意义。本文将声反馈作为在音响扩声系统拾音过程中常见的工作不正常状态来认真研究，利用环路增益分析方法探讨声反馈现象，仔细深入地分析了声反馈产生的本质原因，及基于不同设备的各种抑制处理方法，并对各种方法进行对比，找出各自的优缺点，从而达到综合防治的目的。另外，本文也对实际室内扩声中声反馈现象进行了初步分析讨论，进而完成一个完整的课题研究。

关键词：声反馈；啸叫；环路增益；峰、谷点；

Abstract
The acoustical feedback is refers to a part of the audio frequency signal and the input signal adds to the input end with the same phase, causes the amplitude of some certain frequency continuous enlargement, at last causes certain frequencies shaking. Acoustical feedback caused by the roar not only undermine the entire sound system to the normal working condition, and let the speaker or actor rather agitate for viewers and listeners disappointing let audio equipment operators is very embarrassing. Therefore, the understanding of the acoustic feedback to find better ways to avoid or minimize the roar is very crucial and very important to have practical significance. This article takes the acoustical feedback in the sound amplifying system electric pickup process the common work normal state comes the earnest research, using the loop gain analysis method discussion acoustical feedback phenomenon, has analyzed the essential reason which thoroughly carefully the acoustical feedback produces, and suppresses the processing method based on different equipment's each kind, and carries on the contrast to each method, discovers the respective good and bad points, thus achieves the integrated control the goal. Moreover, this article also carried the acoustical feedback phenomenon on the preliminary analysis to the actual indoor sound amplification to discuss, then completed a complete topic research.

Key words: acoustical feedback; roar; gain; peak , valley point;

目录
第一章  引言……………………………………….  4
第二章  声反馈简介………………………………..  4
2.1 声反馈的形成机理………………………………….  4
2.2 声反馈的形成条件………………………………….  5
2.3 声反馈的危害……………………………………….  7
第三章 室内声反馈分析…………………………….  7
第四章 声反馈的抑制………………………………  11
4.1 物理改变…………………………………………..  12
4.1.1 使音箱的声音不易传到传声器中………………...  12
4.1.2  搞好房间建筑声学设计………………………...   13
4.1.3 合理选用音箱 ………………………………….   13 
4.1.4  合理选用传声器 ……………………………….   14
4.2 防啸叫技术方案实施的原理及优劣对比…………   14
4.2.1 频率均衡方式抑制啸叫…………………………….    15
4.2.2 移频方式抑制啸叫………………………………….    17
4.2.3 移相方式抑制啸叫………………………………….    19
4.2.4 延时方式抑制啸叫………………………………….    19
4.2.5 其他………………………………………………….    20
【总结】……………………………………………………….    21
【致谢】…………………………………………………   22
【参考文献】………………………………………   23