Toa Corporation

Toshimitsu Suetsugu

An object is to provide a public address device that effectively prevents occurrence of howling without a drop of the gain. A public address deviceincludes: a loudspeakerthat generates a reproduced sound on the basis of a loudspeaker driving signal u(n); a microphonethat collects the reproduced sound and an input sound v(n) to generate a microphone-collected-sound signal y(n); a first filterthat generates, on the basis of the loudspeaker driving signal u(n), a pseudo echo signal e(n); an echo-cancelling unitthat obtains a difference between the microphone-collected-sound signal y(n) and the pseudo echo signal e(n) to generate an echo-cancelled signal d(n); a second filterthat whitens the input sound v(n) included in the loudspeaker driving signal u(n); a third filterthat whitens the input sound v(n) included in the microphone-collected-sound signal y(n); a first adaptive filterthat uses, as a reference signal, an output signal output from the second filter, and uses, as a desired signal, an output signal output from the third filter, and estimates a propagation characteristic Wo from the loudspeakerto the microphone; a unit that repeatedly updates a filter coefficient W of the first filteron the basis of a filter coefficient W identified by the first adaptive filter; and a frequency shifting unitthat performs a frequency shift on the echo-cancelled signal d(n) to generate the loudspeaker driving signal u(n).

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Hyogo, Japan

Toshimitsu Suetsugu