A low-delay hybrid noise reduction system includes a reference audio receiving device, an error audio receiving device, an audio output device, and an audio processing device. The audio processing device includes a feedforward noise reduction filter module, a feedback noise reduction filter module, and a mixer. The feedforward noise reduction filter module includes a feedforward least mean squares (LMS) filter, a low-stage finite impulse response (FIR) filter, and 1st to Nth-stage biquad filters. The 1st to Nth-stage biquad filters is set on the input end of the low-stage finite impulse response filter to perform low-delay filtering on the reference source audio signal received and outputs to the low-stage FIR filter so as to output the feedforward noise reduction signal through the low-stage FIR filter.

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.

The noise suppression method of individual active noise reduction system comprises the steps that: (1) initial noise digital signals are received and converted to serve as input signals of a BP neural network; (2) the input signals are processed to generate secondary digital signals; (3) the secondary digital signals are output to a loudspeaker and secondary noise is generated; (4) remained noise digital signals obtained by overlapping the initial noise and the secondary noise are received; whether remained noise digital signals is continuously constant for the set times is judged; if yes, the secondary digital signals are kept outputting; (5) if not, BP neural network parameters are optimized and adjusted with the amplitude of the remained noise digital signals being minimum as the optimality principle; remained noise digital signals of previous step are served as new input signals and the step (2) is executed again.

According to one embodiment, a noise reduction system for reducing noise including impact noise repetitively generated at a time interval includes the following elements. The error signal generator generates an error signal based on the noise being detected. The delay signal generator has a time delay characteristic and delays a signal, which is generated based on the error signal, to generate a delay signal, the time delay characteristic being determined based on an imaging sequence or pre-scanning by the MRI device and corresponding to the time interval. The control filter generates the first control signal from the delay signal. The loudspeaker unit includes at least one pair of a first filter and a control loudspeaker and a transmission unit.

A programmable Active Noise Compensation (ANC) system for an audio input includes a parameter store structured to store a number of various filter parameters. A mode of operation is selected that represents the type of environment the ANC system is operating in—feed-forward, feed-back, or combined feed-forward and feedback. Different filter parameters are retrieved from the parameter store based on the selected mode and desired operation. Audio inputs are sampled at a relatively high sample rate that matches inputs from a feed-forward and feedback microphone that may be present in the system. Parameters and instructions may be changed in the system responsive to changing conditions of the compensation system.

A method of operating a headphone configured to be removed from and placed in close proximity to a user's ear can include generating an input signal by an input signal generating device. The method can also include determining whether an insertion event has occurred based on the generated input signal and causing the headphone to operate in 5 a low power mode responsive to an absence of an insertion event determination after a first period of time. The method can also include causing the headphone to operate in an ultra-low power mode responsive to the absence of an insertion event determination after a second period of time that occurs after the first period of time, the ultra-low power mode having a lower power consumption than the low power mode.

A noise reducing sound reproduction system comprises a loudspeaker that is connected to a loudspeaker input path and that radiates noise reducing sound. A microphone is connected to a microphone output path and picks up the noise or a residual thereof. An active noise reduction filter is connected between the microphone output path and the loudspeaker input path, and the active noise reduction filter comprises at least one shelving filter.

A signal processing device includes a coefficient updater configured to calculate a filter coefficient based on a reference signal, an error signal, and an update parameter to set the filter coefficient in a noise cancelling filter. A parameter adjuster adjusts the update parameter according to fluctuation of the reference signal produced from an output of a reference microphone.

A system and method for converting a passive protector earmuff to a communication and/or active noise reduction (ANR) headset include mounting active components to a frame subassembly configured for insertion into the passive earcup to divide the earcup volume into a front cavity without additional passive leak paths and a back cavity having a volume that improves speaker/driver power efficiency with a resistive vent to atmosphere. An earcup having an external shell includes a frame configured for positioning within the external shell and having a first support adapted to contact an interior of the shell and a second circumferential support cooperating with a seal to contact an ear seal plate of the earcup to form the front and back cavities. The frame may support a speaker between the front and back cavity, and secure circuitry within the back cavity.

A first control signal filter to which a cosine wave oscillating at a control frequency is input; a second control signal filter to which a sine wave oscillating at the control frequency is input; a control signal adder for outputting a control signal generated by adding an output of the first control signal filter and an output of the second control signal filter; a filter coefficient update unit for updating filter coefficients of the first control signal filter and the second control signal filter; and a frequency correction value calculation unit for calculating a frequency correction value for correcting the control frequency on the basis of the control signal and the control frequency.