The technology described in this document can be embodied in a computer-implemented method that includes receiving a portion of a feedback signal of an active noise control (ANC) system, and processing the portion of the feedback signal using an adaptive line enhancer (ALE) filter to detect a tonal signature. The method also includes determining, by one or more processing devices, that the tonal signature represents an unstable condition, and responsive to determining that the tonal signature represents an unstable condition, generating one or more control signals for adjusting one or more parameters of the ANC system, to mitigate the unstable condition.

A first input signal captured by one or more sensors associated with an ANR headphone is received. A frequency domain representation of the first input signal is computed for a set of discrete frequencies, based on which a set of parameters is generated for a digital filter disposed in an ANR signal flow path of the ANR headphone, the set of parameters being such that a loop gain of the ANR signal flow path substantially matches a target loop gain. Generating the set of parameters comprises: adjusting a response of the digital filter at frequencies (e.g., spanning between 200 Hz-5 kHz). A response of at least 3 second order sections of the digital filter is adjusted. A second input signal in the ANR signal flow path is processed using the generated set of parameters to generate an output signal for driving the electroacoustic transducer of the ANR headphone.

A sound control device in a vehicle and control method thereof may include obtaining energy per unit time of an audio signal corresponding to a preset low frequency band, calculating an allowable reference value based on a difference between a magnitude of energy per unit time of the audio signal and a magnitude of a preset maximum allowable input of a speaker, monitoring whether a magnitude of energy per unit time of a noise control signal for eliminating noise in the vehicle exceeds the allowable reference value, and adjusting a magnitude of the noise control signal when the magnitude of energy per unit time of the noise control signal exceeds the allowable reference value.

The improved active noise cancellation system for forced air heating or cooling systems onboard aircraft employs a duct having a proximal end coupled to the fan unit to entrain the airflow stream in the direction of a distal end of the duct. A reference sensor is positioned within the proximal end of the duct. A means is provided for injecting an audio frequency control signal into the airflow stream in a manner that does not substantially impede the airflow stream. An error sensor is positioned at the distal end of the duct where it is responsive to sounds carried by the airflow stream, including the audio frequency control signal. An electronic circuit coupled to the reference sensor and to the error sensor supplies a noise abating control signal to energize the control transducer and thereby substantially reduce at least one noise harmonic of the fan unit through destructive interference.

A sound control device and a method for controlling the sound control device provided in a vehicle. The method comprises obtaining an input signal including at least one of a reference signal of an accelerometer or an error signal obtained from a sound signal of a microphone; adjusting low frequency components of the input signal based on magnitudes of the low frequency components of the input signal and a preset reference magnitude; generating a noise control signal based on the adjusted input signal; and transmitting the noise control signal so that a speaker outputs the noise control signal.

Various implementations include systems for providing enhanced aware mode capabilities in an ANR audio device. In particular implementations, a method includes receiving an ambient noise signal from a microphone associated with a wearable audio device; determining a gain value based on a sound pressure level (SPL) of the ambient noise signal; generating a gain adjusted ambient noise signal by applying the gain value to the ambient noise signal; generating a total external microphone signal by adding the gain adjusted ambient noise signal to a noise reducing ambient signal; generating an expanded audio signal by selectively adjusting a source audio signal based on the gain adjusted ambient noise signal; and combining and outputting the expanded audio signal with the total external microphone signal to an acoustic transducer.

A method of detecting singing of a user of a personal audio device, the method comprising: receiving a first audio signal comprising bone-conducted speech of the user from a first transducer of the personal audio device; monitoring a second audio signal output to a speaker of the personal audio device; and determining whether the user is singing based on the first audio signal and the second audio signal.

A system includes a sound generator (20) that generates sound superimposed to sound to be manipulated. An error sensor (50) measures superimposed sound and outputs a corresponding feedback signal (e′(n)). A signal generator (91) generates a sound signal (y(n)). A controller (92) generates a control signal (λ(n)) representing a value of a sequence of rational numbers. A weighter (93) weights the generated sound signal (y(n)) with the control signal (λ(n)) and inverts it. An adder (94) adds the weighted/inverted sound signal to the feedback signal (e′(n)) and outputs a modified feedback signal (e(n)) to the signal generator (91). A weighter (95) weights the generated sound signal (y(n)) with the difference from one and with the control signal (λ(n)) and outputs the sound signal y′(n). The generated sound signal (y(n)) is a function of the modified feedback signal (e(n)).

Provided are a signal processing device, a program, a range hood device, and a selection method for frequency bins in a signal processing device with which it is possible to reduce the load on computation processing for computing filter coefficients and provide an excellent muting effect even when there are a peak band and a notch band in transmission characteristics from a speaker to an error microphone. A parameter setter sets an update parameter μ such that a filter coefficient W is corrected, only for a first frequency bin that corresponds to a frequency band of a first noise and a second frequency bin that corresponds to a frequency band of a second noise.

A noise-reducing fan system, comprising a motor, a fan body, a plurality of magnetic-inducing elements, a magnetic field generator and a noise-reducing sound source device, is provided. Here, the fan body is mounted on the motor. The fan body comprises a plurality of blades, on which the plurality of magnetic-inducing elements are disposed, respectively. The magnetic field generator, which may generate a magnetic field, is employed for driving the plurality of magnetic-inducing elements to vibrate the plurality of blades and generate a vibration sound, so that at least one portion of the noise emitted from the fan body as rotating may be counterbalanced. The noise-reducing sound source device is disposed on a predetermined position and may send out a noise-reducing sound, so that the noise-reducing sound may counterbalance at least the other portion of the noise emitted from the fan body as rotating.