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Show Method Devised jo Reduce 'Howl' l p.A. Systems neW electronic method de-H de-H bV Bell Telephone Lab-"Afls Lab-"Afls will minimize "howl-jJP "howl-jJP in indoor public address i systems and permit volume to be doubled, W. Mack Lawrence District Manager of the Mountain Moun-tain States Telephone Company said today. The "feedback" or return of room reverbrations to the mic-rophone mic-rophone and thus again to the amplifiers results in a howl Permitting a two-fold increase in-crease in the loudness of a conventional con-ventional p.a. system without mtroducmg howl, the method will also, to a large degree offset variations in amplification amplifica-tion which may be caused by the heating up of amplifiers, different positions of the speakers speak-ers or entertainer, and changes in the listening audience. The new method of countering counter-ing distracting and exagerated room reverbrations is the work of Manfred R. Schroeder. who directs acoustics research at Bell Laboratories. Key to the present development develop-ment is a device called a "frequency "fre-quency shift modulator." Electrically, Elec-trically, it shifts all frequency components of an incoming sound by five cycles per second, an amount that can't be heard for speech and most types of music, Mr. Lawrence, said. |