PURPOSE: To provide a noise reduction device in a vehicle which can prevent effectively and quickly an output exceeding reproducing capability of a loudspeaker.
CONSTITUTION: An Ig pulse is made a primary source PS, the pulse and a filter coefficient W of an adaptive filter 3 are subjected to convolution product- sum operation and outputted from a loud-speaker 8 to a listening point as a cancel sound. A noise reduction state is detected by an error microphone 9 as an error signal and inputted to a LMS operation circuit 5. The LMS operation circuit 5 obtains quantity for correcting a coefficient from the primary source PS and the error signal inputted through a CMN0 circuit 4 and updates the filter coefficient W. On the other hand, an output of the adaptive filter 3 is monitored by an output signal monitoring circuit 6a, comparison between a monitor signal Sm and the maximum output value β is performed by an output signal comparing circuit 6b, an update rate correcting coefficient αis selected from a memory circuit 11b by a α selection setting circuit 11a so that when Sm<β is applied, normal control is performed, and when Sm≥β is applied, a filter coefficient is made smaller, and it is set to the LMS operation circuit 5.
IITAKA HIROSHI
SHIBATA EIJI
