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.

本项目研究数字信号处理系统，以有效地消除咆哮。消除咆哮的一个基本思想是使用自适应陷波来跟踪和抑制咆哮信号，因为它近似为频率未知的正弦信号。本课题的主要研究成果如下：(1)由于相位抖动，实际咆哮信号没有线谱，而是带通谱。为了有效地抑制这种咆哮信号，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检测带通信号通带边缘频率的方法。这种方法在2006年3月的IEICE电路和系统技术小组研讨会上提出。现在它正在准备提交IEICE交易。(2)通过整合前三年的研究，有可能在去年实时取消咆哮信号，这是本项目的最终目标。咆哮消除器被实现为个人计算机上的软件系统，其声音芯片被用作I/O设备。由于自适应系数的收敛性质仍然不理想，因此存在很小的残馀咆哮。但是，如果不使用这个消除器，麦克风放大器就会因为较大的咆哮声而无法正常工作。因此，所设计的咆哮消除器是有效的。现在，更多针对专利申请的增强趋同特性的研究正在进行。