AUTHORS: Ryan D. Reas, Roxcella T. Reas, Joseph Karl G. Salva
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ABSTRACT: Public address system had been in use for a very long time. Since it was first developed, it has evolved from analog public address system to digital public address system. Either analog or digital public address system, its general purpose is to allow efficient communication in a large number of crowd. The object of the public address system is to amplify the received acoustic signal. However, throughout the history of public address system, it had been plagued by problems. One of the problems in public address system is the existence of positive feedback which severely affects the quality output signal. This paper examines the characteristic of acoustic feedback through simulation. The public address system and the acoustic feedback path was based on a low pass finite-impulse-response (FIR) filter. The simulation was performed by increasing slowly the gain of the public address system until the output signal grows exponentially and uncontrollably. The output signal of the public address system with the gain to which it behaves uncontrollably was compared with the output signal of the public address system with a gain 3dB lower. Simulation results show that the acoustic feedback signal has a fixed few narrow frequency components and one of its frequency components dominates the rest of time. Furthermore, it was observed that the public address system with music applied as input acoustic signal and with the existence of acoustic feedback path will have an approximate output signal that is a linear sum of the acoustic feedback signal and music signal. However, the existence acoustic feedback is unpredictable thus its characteristic is hard to quantify. With this, classical way of filtering or signal suppression is inefficient in dealing with the existence of acoustic feedback
KEYWORDS: Feedback, Acoustic Feedback Path, Acoustic Feedback, Howling, Public Address
REFERENCES:
[1] CH Chuang, T. L. (2014). A Hybrid MultiFunction Digital Public Address System WIth Earth Quake Early Warning. 10th International Conference on Intelligent Information Hiding and Multimedia Signal Processing.
[2] Tsung-Hsing Lin, L.-B. C.-H.-L.-H.-C.-L.-L.- W. (Nov. 2013 ). A multi-functions digital public address system for campus broadcasting and security. Global High Tech Congress on Electronics (GHTCE), 2013 IEEE. Shenzhen, China : IEEE .
[3] Kim, J. S. (Nov. 2012 ). Digital public address system with central control using operational MICOM. Soft Computing and Intelligent Systems (SCIS) and 13th International Symposium on Advanced Intelligent Systems (ISIS), 2012 Joint 6th International Conference on. Kobe, Japan: IEEE.
[4] Waterschoot, T. v., & Moonen, M. (Feb. 2011). Fifty Years of Acoustic Feedback Control: State of the Art and Future Challenges. Proceedings of the IEEE, Volume: 99, Issue: 2.
[5] E. Berahl, B. Widrow, and A. E. Flores, 'Acoustic Feedback Cancellation For Public Address Systems,' Stanford University, California, 2005.
[6] Thomas, D., & Jayan, A. R. (Feb. 2014). Automated suppression of howling noise using sinusoidal model based analysis/synthesis. Advance Computing Conference (IACC), 2014 IEEE International. Gurgaon, India: IEEE.
[7] Bispo, B. C., & Freitas, D. R. (Aug. 2014). Evaluation of acoustic feedback cancellation methods with multiple feedback paths. Signal Processing and Multimedia Applications (SIGMAP), 2014 International Conference on. Vienna, Austria: IEEE.
[8] Bispo, B. C., & Freitas, D. R. (Aug. 2014). Evaluation of acoustic feedback cancellation methods with multiple feedback paths. Signal Processing and Multimedia Applications (SIGMAP), 2014 International Conference on. Vienna, Austria: IEEE.
[9] Huang, Z., Huang, D., & Yang, D. (August 2011 ). Research on intelligent acoustic feedback exploration and suppression system. Mechatronics and Automation (ICMA), 2011 International Conference on. Beijing, China : IEEE.
[10] Chen, C. F. (May 1977 ). Detection of acoustical feedback in a public address system. Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '77. (pp. 385-388). Hartford, CT, USA, USA : IEEE.
