Patent ID: 8472637

Claim:
A personal active noise reduction (ANR) device comprising: an acoustic driver; an ANR circuit coupled to the acoustic driver to operate the acoustic driver to acoustically output ANR anti-noise sounds to provide ANR at a location adjacent an ear of a user of the personal ANR device across a range of frequencies having a lower limit and an upper limit; and at least one digital filter of the ANR circuit, wherein: the at least one digital filter is configurable with a plurality of coefficients to implement an ANR transform to derive the ANR anti-noise sounds from ANR reference noise sounds; the ANR circuit is configured to repeatedly reconfigure the at least one digital filter with different pluralities of coefficient values at a first recurring interval to reduce the magnitude of the provision of ANR at one of the lower limit or the upper limit without reducing a magnitude of the provision of ANR across the entire range of frequencies in response to an event adversely affecting the provision of ANR at the one of the lower limit and the upper limit; and the ANR circuit is configured to repeatedly reconfigure the at least one digital filter with different pluralities of coefficient values at a second recurring interval to reverse the reduction in the provision of ANR at the one of the lower limit and the upper limit in response to the event adversely affecting the provision of ANR at the one of the lower limit and the upper limit having ceased.