Detection of acoustical feedback in a public address system

Due to the nature of direct and multiple reflected acoustical paths between microphone and speakers, the frequency of acoustic feedback in a public address(PA) system is unpredictable. The suppression of one particular feedback frequency will result occasionally in the occurrence of another acoustical feedback. The acoustical feedback frequencies of a PA system spread most of the audio range. The creation of feedback due to some perturbation in the media will regenerate and cause further increase of its amplitude. Acoustical feedback in a PA system is a periodic signal. Detection of the acoustical feedback is based on the measurement of time period in one cycle compared with another. A statistical measurement of the above detection must be observed in order to ensure the existence of the feedback signal. In this paper a detailed instrumentation of detecting acoustical feedback over the whole audio range and insertion of a tracking dynamic filter(1) will be described.