Noise cancellation system and signal processing method for an ear-mountable playback device

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.