NOISE REDUCTION DEVICE AND ITS CONTROLLER

摘要

PROBLEM TO BE SOLVED: To provide a noise reduction device capable of always maintaining noise reduction effect at a control point according to sound speed change caused by temperature change, even when a filter characteristic is specified by including a characteristic not affected by the sound speed. SOLUTION: The noise reduction device includes: a coefficient shift filter circuit 11b for generating the signal of a control speaker 2, which generates control sound for reducing noise at the control point C, according to a noise signal; an initial temperature storage circuit 12 for storing an initial temperature T0in which the noise reduction effect becomes maximum at the control point C, when an initial filter coefficient is set to the coefficient shift filter circuit 11b; and a shift number calculation circuit 14 for shifting the filter coefficient by calculating the shift number s of the coefficient shift filter circuit 11b according to time difference between time until noise sound wave reaches a sensor microphone 1 from a noise source S, and time until it reaches the control speaker 2 from the noise source S, according to the initial temperature T0and a current temperature TP. COPYRIGHT: (C)2008,JPO&INPIT