Patent ID: 9031251
Filing Date: 2015-05-12
Classification: G10K,H04R

Abstract:
1. A noise-cancellation device for applying an ambient noise-cancellation (ANC) filter response to electrical signals representing ambient noise, sensed as said ambient noise proceeds toward a listener's ear, to generate further electrical signals and means for transducing said further electrical signals into a modified acoustic signal intended to destructively interfere with said sensed ambient noise when said sensed ambient noise arrives at said ear; the ANC filter response having a gross low-pass filter characteristic and a non-flat pass-band; the device comprising analogue-to-digital conversion means for converting said electrical signals to digital signals, a down-sampling means associated with said analogue-to-digital conversion means and including a gross low-pass filter and a simplified low-pass filter, the down-sampling means configured to implement the gross low-pass filter characteristic, wherein a group delay of the simplified low-pass filter is significantly smaller than a combined group delay of the gross low-pass filter and the simplified low-pass filter, and digital filtering means conditioned to output digital signals for conversion into analogue signals comprising said further electrical signals, the digital filtering means configured to implement the non-flat pass-band; wherein the device is configured such that a first part of said ANC filter response is implemented by said down-sampling means and a second part of said filtering is implemented by said digital filtering means.