Patent ID: 8144888
Filing Date: 2012-03-27
Classification: G10K,G10L

Abstract:
1. An active noise reducing filter apparatus for actively reducing noise d from a primary noise source x, comprising: a secondary source signal connector for connecting to at least one secondary source, such as a loudspeaker, wherein said secondary source generates secondary noise y to reduce said primary noise d; a sensor connector for connecting to at least one sensor, such as a microphone, for measuring said primary and secondary noise as an error signal e; a first delay connected to said sensor connector for delaying said error signal e and a time reversed secondary path filter G* for providing a delayed filtered error signal e′; a reference signal connector for receiving at least one reference signal x, said reference signal x being coherent with said primary noise d; a first control filter W a second delay connected to said reference signal connector for receiving said reference signal x and for calculating a delayed reference signal x′; and an adaptation circuit arranged to adapt said first control filter W wherein the filter apparatus further comprises: a third delay connected to said first control filter W a second control filter W a flatness improving preconditioning circuit for preconditioning the reference signals.