标题: | 声学回声消除系统的设计与实现 Design and Implementation of Acoustic Echo Cancellation (AEC) Techniques |
作者: | 杨镇恳 白明宪 机械工程学系 |
关键字: | 回声;回声消除;Acoustic Echo Cancellation;AEC |
公开日期: | 2006 |
摘要: | 回声消除为免持装置中之一重要部份,负责消除由于同时包含麦克风以及扬声器的系统所导致的回授回音。 早期的回声消除主要是透过设计一些适应性濾波器來达成,但使用这种方法需要很大的运算量。 因此我们利用串接固定系数滤波器与适应性濾波器并采用依据频率范围分段处理来降低非必要的运算量。 此方法可应用在许多方面,例如蓝芽耳机、手机、视讯会议……等。 在适应性滤波器的演算法中,我们采用LMS及NLMS两种演算法,并用消相关滤波器以及次频带法来提高他们的运算速率和效果。 在实验的部份,我们遵照ITU-T Recommendation G.168上的测试方法,并将结果以统计学上的方法MANOVA做判定。 ABSTRACT An acoustic echo cancellation system is presented in this paper. The proposed systems mainly consist of acoustic echo cancellation (AEC) processing and system. The AEC module seeks to reduce the echo resulting from the acoustic feedback in loudspeaker-enclosure-microphone (LEM) systems. In many audio applications, acoustic echo cancellation processing plays an important role when users in video conference or using hands-free system like Bluetooth. The conventional method was used adaptive filters to identify the echo paths adaptively in response to the environmental changes. Besides, we will introduce some other methods, like fixed filter method, hybrid method, sub-band (N)LMS method, block (N)LMS method. In this paper, we combined pure adaptive filter with fixed filter methods to develop hybrid method. Hybrid method has advantages of the above-mentioned two methods and doesn’t have their defects. A parameter, ERLE (Echo Return Loss Enhancement) is used to evaluate the performance, and the standard of performance is referred to ITU standard G .168. A double-talk detection technique is applied to estimate what situation does users in, we can tune the step size of adaptive filter according as the result of double-talk detection to avoid its algorithm diverging. A de-correlation filter is also used alongside sub-band processing to improve the performance and to reduce the complexity of adaptive filter. We will compare all of above-mentioned methods, and approximate total operations of each method. All algorithms are implemented on the platform of a fixed-point digital signal processor (BF533) and a floating-point digital signal processor (SHARC 21364). The process results were recorded for tests and evaluate performance, and presented by Cool-editor. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT009414598 http://hdl.handle.net/11536/80996 |
显示于类别: | Thesis |