聲反饋研究

摘要

聲反饋是指音頻信號(hào)的一部分與輸入信號(hào)同相位地加到輸入端，導(dǎo)致幅度不斷增大而引起某些頻率的震蕩。由聲反饋引起的嘯叫不僅破壞了整個(gè)音響系統(tǒng)的正常工作狀態(tài)，而且讓演員或講話者頗感煩躁，讓觀眾和聽眾掃興，更讓音響設(shè)備的操作員十分尷尬。因此，了解聲反饋并及時(shí)找到較好的辦法來(lái)避免或盡量減少聲反饋引起的嘯叫是非常關(guān)鍵的，具有很重要的現(xiàn)實(shí)意義。本文將聲反饋?zhàn)鳛樵谝繇憯U(kuò)聲系統(tǒng)拾音過(guò)程中常見的工作不正常狀態(tài)來(lái)認(rèn)真研究，利用環(huán)路增益分析方法探討聲反饋現(xiàn)象，仔細(xì)深入地分析了聲反饋產(chǎn)生的本質(zhì)原因，及基于不同設(shè)備的各種抑制處理方法，并對(duì)各種方法進(jìn)行對(duì)比，找出各自的優(yōu)缺點(diǎn)，從而達(dá)到綜合防治的目的。另外，本文也對(duì)實(shí)際室內(nèi)擴(kuò)聲中聲反饋現(xiàn)象進(jìn)行了初步分析討論，進(jìn)而完成一個(gè)完整的課題研究。

關(guān)鍵詞：聲反饋；嘯叫；環(huán)路增益；峰、谷點(diǎn)；

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;

目錄
第一章  引言……………………………………….  4
第二章  聲反饋簡(jiǎn)介………………………………..  4
2.1 聲反饋的形成機(jī)理………………………………….  4
2.2 聲反饋的形成條件………………………………….  5
2.3 聲反饋的危害……………………………………….  7
第三章 室內(nèi)聲反饋分析…………………………….  7
第四章 聲反饋的抑制………………………………  11
4.1 物理改變…………………………………………..  12
4.1.1 使音箱的聲音不易傳到傳聲器中………………...  12
4.1.2  搞好房間建筑聲學(xué)設(shè)計(jì)………………………...   13
4.1.3 合理選用音箱 ………………………………….   13 
4.1.4  合理選用傳聲器 ……………………………….   14
4.2 防嘯叫技術(shù)方案實(shí)施的原理及優(yōu)劣對(duì)比…………   14
4.2.1 頻率均衡方式抑制嘯叫…………………………….    15
4.2.2 移頻方式抑制嘯叫………………………………….    17
4.2.3 移相方式抑制嘯叫………………………………….    19
4.2.4 延時(shí)方式抑制嘯叫………………………………….    19
4.2.5 其他………………………………………………….    20
【總結(jié)】……………………………………………………….    21
【致謝】…………………………………………………   22
【參考文獻(xiàn)】………………………………………   23