US 12,002,447 B2
Noise cancellation system and signal processing method for an ear-mountable playback device
Peter McCutcheon, Goring (GB)
Assigned to AMS AG, Premstätten (AT)
Appl. No. 17/780,733
Filed by ams AG, Premstätten (AT)
PCT Filed Nov. 18, 2020, PCT No. PCT/EP2020/082480
§ 371(c)(1), (2) Date May 27, 2022,
PCT Pub. No. WO2021/104957, PCT Pub. Date Jun. 3, 2021.
Claims priority of application No. 19212145 (EP), filed on Nov. 28, 2019.
Prior Publication US 2022/0415300 A1, Dec. 29, 2022
Int. Cl. G10K 11/178 (2006.01)
CPC G10K 11/17854 (2018.01) [G10K 11/17881 (2018.01)] 17 Claims
OG exemplary drawing
 
1. A noise cancellation system for an ear-mountable playback device having a speaker, a feedforward microphone configured to predominantly sense ambient sound and an error microphone configured to sense ambient sound and sound being output from the speaker, the noise cancellation system comprising
a filter chain for coupling the feedforward microphone to the speaker, the filter chain comprising a series connection or parallel connection of a coarse filter and a fine filter; and
a noise control processor;
wherein
the fine filter is formed of a set of sub-filters;
each of the sub-filters has a predefined frequency range;
the predefined frequency range of each of the sub-filters together forms an effective overall frequency range of the fine filter; and
the noise control processor is configured to
calculate an error signal based on a first noise signal sensed by the feedforward microphone and on a second noise signal sensed by the error microphone;
perform an adaptation of coarse filter parameters of the coarse filter based on the error signal; and
perform a limited adaptation of fine filter parameters of each of the sub-filters based on the error signal, wherein limits of the limited adaptation comprise the predefined frequency ranges of the sub-filters and at least one of a gain limit and a Q factor limit.