Tms320vc5510-based Automatic Sound Feedback Suppressor

Acoustic feedback is a common phenomenon in public addressing systems. Howling, which results from the feedback, restrains the gain increasing and obscures clarity. When feedback goes serious, the public addressing systems even cannot work. Traditional feedback exterminating means include improving rooms'acoustic property, cascading equalizers or frequency-shifters in the sound amplifying link, etc. Nevertheless, these means are inconvenient to operate and cause unnecessary decrease of gain and sound fidelity.Fortunately, great developments in digital signal processing technology over the last decades provide advanced solutions: automatic feedback suppression. It overcomes shortcomings of traditional means, does little harm to desired sounds, improves the gain prominently and is easier to be operated. However, most of automatic feedback suppressors in domestic market are imported from oversea and expensive. We must develop automatic feedback suppressor with own intellectual property to possess enormous competitive strength of marketing.This paper proposes a design of automatic feedback suppressor based on DSP: Firstly, combining FFT algorithm with Chirp-z Transform to detect feedback rapidly and set up the judging conditions based on the feedback characteristics to locate feedback accurately.Secondly, adopting a filter bank composed of 12 IIR narrow-band notch filters to eliminate feedback. 9 fixed filters are used for feedbacks which are inherent in room and 3 dynamic filters are used for new feedbacks when all available filters are in use. All filters are generated by a real-time design algorithm based on detected feedback frequencies to provide better sound quality.Chapter 2 introduces the characteristics of feedback and design targets. Chapter 3 gives the system hardware architecture. Chapter 4 discusses algorithms and implementations. Chapter 5 is the test results.