A method performed by an audio output device is provided for detecting instabilities and taking mitigating actions. Specifically, an A-weighted dBA level of a raw feedback signal exceeding a threshold level trigger, at least, muting the driver. The described methods apply to detecting instabilities across a broad frequency spectrum.

An acoustic measurement system for an industrial process asset includes a process measurement device providing a value representative of an acoustic signal near the industrial process asset based in part on a signal from an acoustic sensor positioned near the industrial process asset. A second acoustic sensor provides an acoustic value and a noise reduction component uses the acoustic value from the second acoustic sensor to affect the value provided by the process measurement device so that the value provided by the process measurement device is more representative of an acoustic signal generated by the industrial process asset.

A headphone detector including a headphone and a processor. The headphone has a microphone and a speaker, and the microphone is configured to generate an audio signal based on an output of the speaker. The processor is configured to receive the audio signal, determine a characteristic of the audio signal, and assess whether the headphone is on ear or off ear based on a comparison of the characteristic to a threshold. The threshold corresponds to one or more of an audio response of the audio signal at a corresponding frequency and an audio response of a feedback microphone signal at a corresponding frequency, under one or more known conditions.

An active vibration and noise control device robust against outside disturbances, and an active vibration and noise control circuit are provided. An adaptive control circuit of this active vibration and noise control device has autocorrelation value calculation units which calculate an autocorrelation value of an error signal or of a target signal, which is a reference signal or a standard signal, and a canceling output limiting unit which determines whether or not an autocorrelation value is less than an autocorrelation threshold value, and limits increases in the cancelling output if it is determined that the autocorrelation value is less than the autocorrelation threshold value.

A system (70) for actively controlling sound propagating through exhaust systems (40) includes a controller (90), a sound generator (30), in fluid communication with an exhaust system (40), and an actuator (20), inside the sound generator and receiving a controller control signal for generating sound inside the sound generator to reduce sound inside the exhaust system. The controller identifies an increased exhaust pressure inside the exhaust system based on signals output by an error microphone (50), a temperature sensor (51), an impedance measuring bridge (52), a bus system (53), or a water sensor (54). The controller interrupts a generation of the control signal and/or interrupts an output of the control signal to the at least one actuator and/or reduces a level of the control signal output to the at least one actuator by at least 30% or at least 60% upon determining a presence of an excessive exhaust gas pressure.

The handling of disturbances to audio signals may be improved with an adaptive noise cancellation (ANC) system that performs tone suppression and howl suppression in a collaborative manner. Such ANC systems may be configured to detect a first tone in an input signal at a first tone frequency and extract the detected first tone from the input signal. The ANC systems may also be configured to adaptively filter the extracted first tone to generate a second tone that has a magnitude that is approximately equal to a magnitude of the extracted first tone and a phase that is approximately opposite the phase of the extracted first tone. The ANC systems may be further configured to add the second tone to an intermediate signal that is based, at least in part, on the input signal to generate the output signal.

A method and system for a noise cancellation comprises an amplifier in communication with the three or more speakers disposed in an area. A system controller produces a driver signal for each of the speakers in response to a signal from at least one microphone detecting sound in the area and communicates the driver signals to the amplifier. The amplifier drives each speaker with the driver signal produced for that speaker. In response to the driver signals, the speakers emit sound that combined produces a substantially uniform sound pressure field for a particular zone within the area. The substantially uniform sound pressure field produced by the speakers has a magnitude and phase adapted to attenuate a noise field in the area corresponding to the sound detected by the at least one microphone.

An example active road noise control includes generating with a sensor arrangement a primary sense signal representative of at least one of accelerations, motions and vibrations that occur at a first position, and providing a noise reducing signal by processing the primary sense signal according to an adaptive mode of operation or a non-adaptive mode of operation. It further includes generating within the vehicle body noise reducing sound at the second position from the noise reducing signal, evaluating the primary sense signal and controlling the processing of the primary sense signal so that the primary sense signal is processed in the adaptive mode of operation when the magnitude of the primary sense signal undercuts a first threshold and in the non-adaptive mode of operation when the magnitude of the primary sense signal exceeds a second threshold, the first threshold being equal to or smaller than the second threshold.

A system includes a first earpiece having an earpiece housing configured to isolate an ambient environment from a tympanic membrane by physically blocking ambient sound, a microphone disposed within the housing and configured to receive a first ambient audio signal from the ambient environment, a processor operatively connected to the microphone wherein the processor is configured to receive the first ambient audio signal from the microphone and determine if the first ambient signal exceeds a threshold sound level, and a speaker operatively connected to the processor. In a first mode of operation the processor determines the first ambient audio signal exceeds the threshold sound level and processes the first ambient audio signal to modify the first ambient audio signal. In a second mode of operation the processor determines the first ambient audio signal does not exceed the threshold sound level and reproduces the first ambient audio signal at the speaker.

The handling of disturbances to audio signals may be improved with an adaptive noise cancellation (ANC) system that performs frequency-domain adaption. The ANC systems may be configured to determine if a disturbance is present at a first frequency in the second input signal received from the reference microphone. The ANC systems may update an algorithm of an adaptive filter based, at least in part, on the first input signal, the second input signal, and a feedback signal that is based on an output of the adaptive filter by changing parameters of the algorithm such that the adaptive filter adapts around the first frequency differently than other frequencies when the disturbance is present.