Sophisticated Adaptive Signal Processing Systems for Howling Canceller

用于啸叫消除器的复杂自适应信号处理系统

• 批准号: 14550372
• 负责人: WATANABE Eiji
• 金额: $ 2.24万
• 依托单位: Shibaura Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550372/
• 关键词: Howling; Adaptive notch filter; Variable filter; Digital filter; Filter design; Adaptive signal processing; Digital signal processing; Discrete-time system

This project investigates digital signal processing systems for canceling howling efficiently. A fundamental idea to cancel howling is to use adaptive notch filters to track and reject howling a signal because it is approximately a sinusoid whose frequency is unknown. Main results of this project are as follows ;(1)An actual howling signal does not have a line spectrum but a bandpass one due to phase jitter. In order to reject such a howling signal efficiently, it is required to detect its width and to determine the bandwidth of an adaptive notch filter. Then a method for the detection of passband edge frequencies of a bandpass signal by using a second-order adaptive notch filter has been proposed. This method was presented IEICE Technical Group Workshop on Circuits and Systems on March 2006. Now it is in preparation to submit IEICE Transactions.(2)By integrating the studies in early three years it became possible to cancel howling signals in real time in last year, which is the end goal of this project. The howling canceller is realized as a software system on a personal computer, whose sound chip is used as an I/O device. Since the convergence property of an adaptive coefficient is not still perfect, very small residual howling exists. However, when this canceller is not applied, microphone amplifiers cannot work well due to large howling. Therefore, the designed howling canceller is effective. Now more studies to enhance the convergence property is doing toward patent filings.

该项目研究有效消除啸叫的数字信号处理系统。消除啸叫的基本思想是使用自适应陷波滤波器来跟踪和抑制啸叫信号，因为它近似于频率未知的正弦曲线。本课题的主要研究成果如下：(1)由于相位抖动，实际的啸叫信号不具有线谱，而是具有带通谱。为了有效地抑制这种啸叫信号，需要检测其宽度并确定自适应陷波滤波器的带宽。然后提出了一种利用二阶自适应陷波滤波器检测带通信号的通带边缘频率的方法。该方法于2006年3月在IEICE技术组电路与系统研讨会上提出，目前正在准备提交IEICE Transactions。(2)通过整合前三年的研究成果，去年实现了实时消除啸叫信号，这是该项目的最终目标。啸叫消除器作为个人计算机上的软件系统实现，其声音芯片用作I/O设备。由于自适应系数的收敛特性还不完善，因此存在非常小的残余啸叫。然而，当不应用这种消除器时，麦克风放大器由于较大的啸叫而无法正常工作。因此，所设计的啸叫消除器是有效的。现在，更多旨在增强收敛性的研究正在针对专利申请进行。