Abstract: The present invention provides an active control type noise reducing device that is disposed at a sound barrier and with which can be obtained an excellent noise reduction effect with respect to moving sound sources. Linear array of flat loudspeakers are arranged in ascending order from an incoming side of automobiles towards an outgoing side. Delay times of 0, ?, 2?, . . . , 8? are respectively given in the arrangement order to the linear array of flat loudspeakers. By delaying signals in correspondence to the arrangement order, the wavefront of a control sound can be slanted in a diagonal direction. Namely, “line sound sources”, where sound sources are linearly arranged, arc pseudo-realized.

Abstract: Effective reduction is made of direct sound or diffracted sound of a noise propagating from plural directions. Three microphones (18k?1, 18k, 18k+1) are disposed and: noise is detected by each of the microphones; delay signals are generated by delaying plural times a signal that has been output from 2 of the microphones (18k?1, 18k+1); the output signal from the remaining microphone (18k) is added to 2 of the delayed signals and input to respective speakers of a speaker unit; a control sound is output from the speaker unit in 3 directions (L, C, R); and reduction is made of direct sound or diffracted sound of a noise propagating from each of the directions.

Abstract: The present invention provides an active control type noise reducing device that is disposed at a sound barrier and with which can be obtained an excellent noise reduction effect with respect to moving sound sources. Linear array of flat loudspeakers are arranged in ascending order from an incoming side of automobiles towards an outgoing side. Delay times of 0, ?, 2?, . . . , 8? are respectively given in the arrangement order to the linear array of flat loudspeakers. By delaying signals in correspondence to the arrangement order, the wavefront of a control sound can be slanted in a diagonal direction. Namely, “line sound sources”, where sound sources are linearly arranged, arc pseudo-realized.