NOISE REDUCTION METHOD IN CLOSED SPACE, AND NOISE REDUCTION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a noise reduction system for actively cancelling all sounds in a closed space where a number of reflection sounds are superposed on noise.SOLUTION: The noise reduction system includes: a microphone 1 which collects a sound within a room that is a closed space, and generates a first acoustic signal S1 representing the sound; band pass filters 21-2N each having a predetermined bandwidth defining a resonant frequency for each mode of separately calculated standing waves within the room as a central frequency, for extracting specific frequency components from the first acoustic signal S1, respectively, and generating second acoustic signals S21-S2N; phase adjusting means 31-3N for adjusting phases and gains of the second acoustic signals S21-S2N for generating third acoustic signals S31-S3N cancelling the standing waves, respectively; an adder 4 which adds the third acoustic signals S31-S3N, respectively, to generate a fourth acoustic signal S41; and a speaker 6 which emits cancellation sounds of the standing waves into the room on the basis of the fourth acoustic signal S41.