An active noise cancellation (ANC) system may include an adaptive filter divergence detector for detecting divergence of the one or more controllable filters as they adapt, based on dynamically adapted thresholds. Upon detection of a controllable filter divergence, the ANC system may be deactivated, or certain speakers may be muted. Alternatively, the ANC system may modify the diverged controllable filters to restore proper operation of the noise cancelling system.

A safe earphone includes a wired safe earphone and an over ear safe headphone, having plurality of speakers with different frequency responses respectively used for two ears to listen, so the frequency response is particularly good; it is provided with a noise reduction signal conversion system which effectively converts the transmission of the active noise reduction frequency signal into the transmission of the passive audio signal and then restore to the transmission of the active audio signal after transmission of 1000 mm in length, therefore human body is isolated from radiation of communication at a long distance, which achieves a good a high degree of radiation protection, and solving the technical problem that the microphone of the existing radiation-proof earphone must be placed outside the air tube. Therefore, the invention is an excellent safe earphone achieving highly radiation-proof, having high sound quality and noise reduction function.

Various aspects include a wearable audio device having active noise reduction (ANR). In some cases, an ANR system for a wearable audio device includes: a fixed filter that receives a signal from a feedback microphone and outputs a noise reduction signal, where the fixed filter is configured to provide ANR with a nominal loop gain; and a tunable filter that outputs an adjusted noise reduction signal by modulating the nominal loop gain in response to low frequency noise being detected in the noise reduction signal, where modulating the nominal loop gain includes reducing low frequency ANR performance.

A vehicle and an associated method for augmenting audible sound generated in a passenger compartment by operation of first and second torque machines are described. The passenger compartment includes an audio speaker that is operably controlled by a controller that is also is in communication with the first and second torque machines. The controller includes an instruction set that is executable to determine first parameters associated with audible sound generated by operation of the first torque machine and determine second parameters associated with audible sound generated by operation of the second torque machine. A desired audible sound in the passenger compartment is determined. The audio speaker is controlled to generate a correction tone based upon the first parameters, the second parameters and the desired audible sound in the passenger compartment.

A vehicle and an associated method for augmenting audible sound generated in a passenger compartment by operation of first and second torque machines are described. The passenger compartment includes an audio speaker that is operably controlled by a controller that is also is in communication with the first and second torque machines. The controller includes an instruction set that is executable to determine first parameters associated with audible sound generated by operation of the first torque machine and determine second parameters associated with audible sound generated by operation of the second torque machine. A desired audible sound in the passenger compartment is determined. The audio speaker is controlled to generate a correction tone based upon the first parameters, the second parameters and the desired audible sound in the passenger compartment.

A noise-cancellation system, including: a noise-cancellation filter configured to generate a noise-cancellation signal; an actuator configured to receive the noise-cancellation signal and to transduce a noise-cancellation audio signal based on the noise-cancellation signal, the noise-cancellation audio signal destructively interfering with an undesired noise in a noise-cancellation zone in a predefined volume; an error sensor configured to output an error sensor signal, the error sensor signal being representative of residual undesired noise in the noise-cancellation zone; a performance cost filter configured to receive and filter the error sensor signal and to output a performance cost filter signal, the performance cost filter signal being representative of the error sensor signal as weighted by a performance cost function; and an adjustment module configured to receive the performance cost filter signal and to adjust the noise-cancellation filter such that the noise-cancellation audio signal minimizes the performance cost filter signal.

Active noise-cancelling (ANC) headphones in the form of a part of a headset or as in-ear headphones that reduce acoustic adaptation by providing an electrodynamic speaker in a housing with ventilation openings and an acoustically permeable front panel. These components form a module that can be integrated into ANC headphones, permitting its installation in different headphones without customization. The module reacts to a reduction of the impermeability situation in such a manner, that an impedance change of the speaker takes place below 100 Hz. For example, a microphone and electronics with a feedback filter for active noise cancellation can be provided that form a secondary route between speaker and microphone. In a further development, an evaluation unit is provided which detects and evaluates a change in the impedance of the speaker and adapts the feedback loop.

Disclosed is a system, method, and aircraft for controlling acoustic radiation from an aircraft comprising a plurality of rotor systems and a noise controller configured to regulate acoustic radiation from the plurality of rotor systems. The noise controller can be configured to regulate a commanded flight setting from the flight control system and to output a regulated flight setting to the plurality of rotor systems. Based on the regulated flight setting, the plurality of rotor systems are configured to generate, individually and in aggregate, acoustic radiation having a target acoustic behavior. In certain aspects, the noise controller can change the directionality of acoustic radiation from the plurality of rotor systems, or otherwise tune the acoustic radiation to reduce detectability or annoyance.

A sound output apparatus of a vehicle may include a sensor sensing a driving speed of the vehicle and a number of revolutions of a driving motor, a storage storing opposed-phase sound sources of a noise according to the number of revolutions of the driving motor, and a controller allowing an opposed-phase sound source corresponding to the number of revolutions of the driving motor, from among the opposed-phase sound sources stored in the storage to be output when the driving speed of the vehicle exceeds a predetermined speed.

An in-ear active noise reduction earphone includes a housing, and the housing includes a rear chamber and a front chamber, and the housing is laterally provided with a sound generating unit separating the rear chamber from the front chamber; the rear chamber is located at a top of the housing, a feedforward microphone is installed inside the rear chamber, the front chamber is located at a bottom of the housing, and a feedback microphone is installed inside the front chamber; and the front chamber includes a first front chamber and a second front chamber, and the feedback microphone is installed inside the second front chamber.