Effect Of Adaptation Constant Μ In The Achievable Amplification Of A Real Time Lms Based Adaptive Feedback Canceller For Public Address System
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This study considers the problem experienced with public address system in an area constrained environment. In an environment wherein public address system is used to address the general public, acoustic feedback occurs unpredictably which significantly degrades the acoustic quality of the information signal. An adaptive filter is then presented, with the objective to reduce the effect of acoustic feedback of the public address system that might occur at any point within the area. The system covers a 20th order multi-tapped finite impulse response (FIR) adaptive filter that is implemented in field programmable gate array (FPGA). The performance of the adaptive filter with least mean square (LMS) adaptive algorithm was presented and the effects of the adaptation constant μ were investigated. The system was evaluated with a prepositioned speaker and microphone to which an acoustic feedback would occur by slowly increasing the gain of the audio power amplifier. An acoustic signal was also applied to a microphone as part of the evaluation. During an evaluation, the acoustic activity of the environment was observed by a spectrum analyzer and spectrograph. Results show that with large μ, the adaptive filter was able to quickly reduce the howling signal before the system exhibit an unstable behavior. However, results also show that the magnitude of the output information signal of the public address system with large μ is lesser compared to a smaller μ of the adaptive filter. This shows that the adaptation constant μ does not only eliminate the acoustic feedback but also reduces the amplification of the public address system with acoustic feedback controller.
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