| Abstrakt: |
A procedure for reducing feedback in sound systems and controlling room-ring modes is described. Narrow-band antiresonant passive filters are introduced in the link circuit(s) (LC) of the amplifier, each LC being tuned to the frequency of the particular mode to be controlled. Depth of notch is regulated by taps on the high-Q inductor of the filter. Usable system gain before feedback is increased and smoothness of the house curve of SPL versus frequency is improved. Experimental observations in some fifty large rooms with sound systems indicate that, in highly reverberant rooms such as churches, the number of self-oscillatory modes and ring modes that interfere with speech intelligibility is limited. If a room-ring mode has the same frequency as a feedback mode, narrow-band insertion losses of as much as 30 dB may be required. Otherwise, notch depths of 3-10 dB or so are normal. Observations are reported on the priority order of the modes, effect of microphone position, beating modes, and other phenomena that have been encountered. [ABSTRACT FROM AUTHOR] |
