US Patent 8208650 Feedback-based ANR adjustment responsive to environmental noise levels

An ANR circuit, possibly of a personal ANR device, monitors a sound level of environmental sounds detected by a microphone external to an earpiece in which the ANR circuit is providing feedback-based ANR, and increases or decreases the degree of feedback-based ANR provided in response to the external microphone detecting a higher or lower sound level, respectively. Increasing and decreasing the degree of feedback-based ANR provided may be carried out by changing a variable loop gain of the ANR circuit and/or a range of frequencies of environmental sounds attenuated by the feedback-based ANR.