科技英语课程
论文（报告、案例分析）
院系物理与电子工程学院
专业电子信息工程
班级电工211班
学生姓名刘脐中
学号 2012128041
任课教师罗倩倩
2014年 12 月 9日
Howling suppression system report
Liu Qizhong
Electronic and Information Engineering
Hubei University of Arts and Science
1454814125@
Abstract：The class D power amplifier based on TPA3112D1 TI, to collect speech signal pre omnidirectional microphone,
Through the signal extraction, filter, power amplifier and other processing,through a 8 ohm 5W horn sound output, and through the whistle frequency detection circuit feedback, by higher order program control wave trapLTC1068-25, complete the howling detection, howling suppression and powercalculation and other functions, the higher system efficiency.
Key words：Class D power amplifier;Detection of squeal frequency;Programmable notch filter
1 Introduction
TI power amplifier chip based on TPA3112D1, audio amplifier design andmake a howling detection and suppression function, complete desktopmicrophone amplifies the audio signal through the power amplification circuit to send the speaker output.To further improve the howling suppression circuit. In the precondition of ensuring no whistling, try to improve audio power.The output power of the amplifier.
2 Materials and Methods
The final selection of the STM32 as the main control chip, the selectionreason: compared with STM32, TI M4 ARM also Coretex architecture based on80M clock, timer, but poor stability, and no built-in DA, difficult to meet the requirements, so the final system using STM32 as the MCU unit.
3 The Improved Method
3.1 Method one
With three tubes, by reasonably setting the static working point, to the electretseries resistance equivalent resistance,
Dynamic voltage by capacitance coupling mode to acquisition the electret microphone at both ends, to achieve a more sensitive collection effect, also a certain degree of noise suppression.
3.2Method two
Using operational amplifier noninverting input capacitance coupling mode,using the high input impedance, to collect speech signal, while suppressing the purpose of dynamic noise.
3.3Discussing about method one
A scheme of low cost, but the pickup effect is not clear, the selection of LM358special audio amplifier chip, can better do front audio amplification, the choice of scheme two.
4 Conclusion
This system to suppress squeal core to notch, with three grade for different values of Q notch filter cascade, real-time tracking of input signal of whistlers,complete suppression, effect is good, the two howling suppression is better,the shortage is that: the system stability is poor, at all levels of the connectionis more complex, especially MCU peripheral connection is not stable, also need to be greatly improved. Consider other occupy part of interrupt, the keyreaction is slow control power, the need to improve.
References
[1] (Tong Shibai)2006
[2](,2)2008
[3] (Sun Xiaozi )2006
