Design And Implementation Of Acoustic Feedback Suppresser Based On DSP

When a loudspeaker and a microphone are placed within an enclosure, Howling is often found in sound-amplifying systems, which results from acoustic feedback. It restrains sound-amplifying system's gain from increasing. Acoustic feedback suppresser is necessary in conference system. When feedback is serious, the sound-amplifying systems even can not work. The AFS has two main functions: eliminating the echoes due to acoustic feedback from loudspeaker to microphone and protecting the communication systems from howling and becoming stable when this kind of feedback becomes serious. Traditional acoustic feedback suppressing methods consist of improving room's acoustic property. Cascading an equalizer or a frequency-mover in the sound amplifying link, etc. These methods hurt the normal sound, only improve the system gain a little and are not easy to operate.Recently, digital signal processing technology develops greatly. A new generation of acoustic feedback suppresser appears. It overcomes old feedback suppressers' shortcomings, does little harm to speech and music signals, improves the systems' gain prominently and is easy to operate. Nowadays, most of the acoustic feedback suppressers available are imported from oversea, which are expensive, such as dbx advanced feedback suppresser 224.If we develop a feedback suppresser with intellectual property which can replace foreign products, we can apply it in multimedia classrooms, meeting rooms, etc.Based on the application ground, we put forward a scheme for acoustic feedback suppresser.This scheme is particular in the following aspects:Firstly, in order to meet the need of conference system, we adapt modern spectrum estimation to analyze signals and get the frequency happening acoustic feedback precisely. The system's frequency resolution can obtain within 1 Hz.Secondly, we adapt an algorithm suitable for designing IIR filter on DSPs. The algorithm can design high frequency-selective IIR filters.Thirdly, In order to estimate the frequency of acoustic feedback and realize IIR filter accurately, we choose the float processor TMS320C6711.