A system for detecting divergence in a noise-cancellation system, comprising: a controller configured to: determine a power of a component of the error signal, the component being correlated to the at least one reference sensor signal; determine an average value, over a first time period, of a value representative of a time gradient of the power of the component of the error signal; and determine whether the average value is greater than a threshold.

Aspects are generally directed to headphone systems that adjust Active Noise Reduction operations based on measurements of environmental conditions. In one example, a headphone system includes an earpiece having an interior volume, the earpiece configured to couple to an ear and define an acoustic volume including the interior volume and a volume within the ear, a speaker to provide acoustic energy to the acoustic volume based on a received driver signal, a feedback microphone to detect at least residual noise within the acoustic volume and generate a feedback audio signal indicative of the residual noise, and a control circuit including a sensor interface configured to receive an atmospheric pressure signal, the control circuit coupled to the feedback microphone to receive the feedback audio signal, and the control circuit configured to adjust the driver signal based at least in part on the feedback audio signal and the atmospheric pressure signal.

An apparatus includes a noise reduction headphone comprising one or more microphones and an acoustic transducer, the one or more microphones configured to generate an input signal; and a controller comprising one or more processing devices, the controller configured to: process the input signal through one or more noise reduction filters to generate a noise-reduction signal, compare the input signal to an estimate of ambient noise to determine if the energy of the input signal is greater than the estimate of ambient noise, wherein if the energy of the input signal is greater than the estimate of ambient noise by a predetermined amount, a change in the noise reduction signal is suppressed; and generate an output signal, the output signal comprising, at least in part, the noise-reduction signal, wherein the acoustic transducer is configured to produce an acoustic output in accordance with the output signal.

A playback audio signal is combined with a feedback signal from a feedback microphone to provide a first combined signal. The first combined signal is filtered with a feedback filter to provide a driver command signal. The driver command signal is provided to an acoustic transducer for transduction to acoustic energy. The first combined signal is compared with the feedback signal to detect a feedback instability based upon the comparison.

The application describes techniques for howling detection. A processing module for a noise control circuit is described. The processing module comprises a howling detector configured to receive an input signal and to determine a log-linearity metric based on the input signal. Gain adjustment of the noise control unit following the detection of howling is also described, wherein the amount of gain adjustment may be based on an estimation of the maximum stable gain of the noise control unit.

Audio devices and methods are provided for detecting instability in an associated feedforward audio processing system. A microphone provides a feedforward signal for processing by a feedforward filter. The processed signal may provide noise reduction and/or sound enhancement associated with the surrounding environment. The processed signal contributes to a driver signal provided to an acoustic transducer, e.g., a driver, to produce acoustic signals for a user. A processor is configured to detect an indication of instability in one or more of the signals, and to adjust a phase response of the feedforward signal path in response to detecting the indication of instability.

An audio system attachable to a computer includes a sound reproduction device for producing audible sound from audio signals. The sound reproduction device includes a radio tuner and a powered speaker. The audio system further includes a connector for connecting the sound reproduction device with a computer. The computer provides audio signals from a plurality of sources, the sources including a computer CD player, digitally encoded computer files stored on the computer, and a computer network connected to the computer. The sound reproduction device further includes control buttons for controlling at least one of the computer CD player, the digitally encoded computer files and the computer network.

Aspects include approaches for feedback instability control in wearable audio devices. In certain cases, a method of controlling feedback instability in a wearable audio device with an active noise reduction (ANR) system includes: determining a current feedback instability by combining outputs from multiple instability detectors, applying latch logic to the current feedback instability to determine a current mitigation value, and adjusting a driver command signal based on the current mitigation value to mitigate feedback instability.

A personal audio device, such as a wireless telephone, includes noise canceling circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone may also be provided proximate the speaker to estimate an electro-acoustical path from the noise canceling circuit through the transducer. A processing circuit uses the reference and/or error microphone, optionally along with a microphone provided for capturing near-end speech, to determine whether one of the reference or error microphones is obstructed by comparing their received signal content and takes action to avoid generation of erroneous anti-noise.

An active road-noise control system and method include using a sensor arrangement to generate a first sense signal representative of at least one acceleration, motion and/or vibration that occurs at a first position on a vehicle body and a second sense signal representative of sound that occurs at a second position within the vehicle body; they also provide a noise-reducing signal by processing the sense signals according to a first or a second mode of operation. They include the generation of noise-reducing sound within the vehicle body at the second position from the noise reducing signal and the operational state of the sensor arrangement; the first sense signal and the second sense signal are processed in the first mode when the sensor arrangement is in a proper operational state and in the second mode when a malfunction of the sensor arrangement has been detected.