13 results about "Noise power spectrum" patented technology

The present application relates to the technical field of noise processing, and discloses a noise whitening method, device, equipment and storage medium, the method comprises the following steps: constructing an error function based on an equalization signal and a training sequence; calculating based on the error function to obtain gradient information; updating the tap coefficient of the noise whitening filter based on the gradient information to obtain a target tap coefficient; whitening the colored noise based on the target tap coefficient. The present application updates the tap coefficient of the noise whitening filter by formulating the error function and calculating the gradient, solves the problem that when the channel equalization technology is used to overcome the bandwidth limitation, the equalization enhances the colored noise, leads to uneven noise power spectrum, and thus reduces the IM-DD transmission rate, realizes the whitening of the colored noise, makes the power spectrum flat, and thus significantly improves the performance of the IM-DD system and increases the communication capacity.

The application discloses a laser phase noise measurement method based on delay self-heterodyne and digital demodulation, and relates to the technical field of laser measurement, and comprises the following contents: after being adjusted by a variable optical attenuator, to-be-measured laser is divided into a frequency shift arm and a delay arm, the frequency shift arm is frequency-shifted by an acousto-optic modulator, the delay arm is delayed by a delay optical fiber, and original electric beat frequency signals are obtained by a balanced photoelectric detector after the two arms are coupled; homologous and synchronous quadrature demodulation is carried out on the original electric beat frequency signals, envelope credibility judgment and abnormal sample repair are combined, and a continuous differential phase sequence is obtained; actual optical time delay is determined according to the beat frequency spectrum characteristics and the continuous differential phase sequence, and a differential phase power spectral density is formed; then, transmission relationship conversion is carried out according to the actual optical time delay, bounded spectrum compensation is implemented on a zero point neighborhood and a low credibility frequency point, and an intrinsic phase noise power spectral density is obtained. The application can improve the stability, continuity and result credibility of phase noise measurement under the condition of short delay.

This invention belongs to the field of noise floor reduction and proposes a frequency-band noise floor reduction method based on a spectrum analyzer. This invention can solve the problems of uneven noise power distribution and excessive noise power estimation. It includes the following steps: acquiring the noise floor signal of the spectrum analyzer, wherein the noise floor signal is a low-pass or band-limited white noise signal with a specified bandwidth; dividing the specified bandwidth into a first number of sub-segments and dividing the signal power before denoising into a first number of sub-segments; estimating the noise power under the specified bandwidth and dividing it into a first number of sub-segments; denoising each sub-segment and calculating the noise power spectral density of each sub-segment after denoising based on the bandwidth after segmentation, the signal power before denoising after segmentation, and the estimated noise power after segmentation; and ensuring that the noise power spectral density after denoising is not negative by using the compression factor method or the square root method.

The application discloses a ship radiated noise power spectrum measurement method based on frequency difference beam forming, comprising the following steps: obtaining a to-be-measured radiated noise signal received by a base array; constructing a difference frequency signal through the conjugate product of the to-be-measured radiated noise signal and a reference frequency signal; performing beam forming on the constructed difference frequency signal based on the difference frequency, and calculating the amplitude of the beam output signal of the difference frequency signal; correcting the amplitude of the beam output signal of the difference frequency signal by using the amplitude of the reference frequency signal to obtain the amplitude of the to-be-measured radiated noise signal, and calculating the power spectrum of the to-be-measured radiated noise signal. The application converts the signal outside the design frequency band of the base array to the inside of the design frequency band to perform beam forming, improves the array gain, better suppresses the environmental noise, improves the measurement performance of the base array on the radiated noise outside the design frequency band, greatly expands the frequency band width of the ship radiated noise measurement, and can realize the measurement of the radiated noise with a larger bandwidth by using a smaller aperture array.

A system and method of harmonizing computed tomography (CT) images to reduce variability introduced by differing reconstruction kernels. The method includes acquiring a CT image of a plurality of regions of a patient. The method includes calculating, by a processing device, a noise power spectrum (NPS) of a uniform region among the plurality of regions. The method includes selecting, from a library of reconstruction kernels, a first reconstruction kernel based on the NPS of the uniform region of the plurality of regions. The method includes generating a harmonized CT image based on the first reconstruction kernel and the CT image.

The invention discloses a power delay spectrum estimation method based on frequency domain noise whitening, which is applied to a power line communication system. According to the method, in order to solve the problems that power line channel frequency selective noise is high and a special silence period is lacked, the noise power spectral density is directly estimated from a received signal through frequency domain smoothing processing, a frequency domain whitening filter is designed according to the noise power spectral density to conduct whitening and normalization processing on channel response, the frequency selective noise is converted into flat noise, and the frequency selective noise is obtained. And a power delay spectrum with a substantially reduced noise floor is generated. On the basis, multipath components are accurately recognized through peak detection and parameter estimation, signals are reconstructed to separate and calculate signal and noise power, and finally high-precision signal-to-noise ratio estimation is achieved. According to the method, a silent period is not needed, frequency selective noise can be effectively resisted, and the accuracy of multipath parameter and signal-to-noise ratio estimation is remarkably improved.

The invention discloses a post-filtering method for an audio signal, and relates to the technical field of audio signal processing, and the technical scheme of the invention comprises the following steps: determining an initial first posterior signal-to-noise ratio based on a beam output signal and an estimated noise power spectral density value, and determining an initial first prior signal-to-noise ratio based on the first posterior signal-to-noise ratio; determining an initial first post-filtering weight according to the first prior signal-to-noise ratio, and performing preliminary noise suppression on the beam output signal by using the first post-filtering weight to obtain an intermediate processing signal; determining an optimized second posterior signal-to-noise ratio based on the intermediate processing signal and the noise power spectral density value, and determining an optimized second prior signal-to-noise ratio based on the second posterior signal-to-noise ratio; and determining an optimized second post-filtering weight according to the second prior signal-to-noise ratio, and performing post-filtering processing on the beam output signal based on the second post-filtering weight. According to the invention, residual noise can be suppressed more accurately and effectively.

The invention discloses an intelligent hearing aid noise reduction method combined with environmental noise evaluation, and relates to the technical field of hearing aid signal processing, comprising the following steps: collecting an audio signal and converting the audio signal to a frequency domain to obtain a frequency domain signal; extracting noise features from the frequency domain signal, calculating a noise time-varying index and spectrum flatness, and identifying an environmental noise type; estimating a noise power spectrum, determining a noise tracking parameter according to the environment noise type, and updating the noise power spectrum; calculating a signal-to-noise ratio parameter corresponding to the noise power spectrum, determining a noise reduction intensity factor according to the environmental noise type and the hearing characteristics of the user, and calculating a noise reduction gain based on the signal-to-noise ratio parameter and the noise reduction intensity factor; and performing noise reduction processing on the frequency domain signal by using the noise reduction gain, and converting the frequency domain signal to a time domain to output a processed audio signal. According to the invention, the noise tracking parameter is adaptively adjusted by identifying the environmental noise type, and the noise reduction intensity is determined in combination with the hearing characteristics of the user, so that the noise reduction effect and the user suitability of the hearing aid in a complex environment are improved.

The application discloses a noise estimation method and related device, the method comprises the following steps: obtaining the audio to be processed; processing the audio to be processed to obtain the power spectrum and the noise power spectrum of the audio to be processed; comparing the noise estimation value of each frame signal of the audio to be processed at each frequency point with the minimum power value of each frame signal at each frequency point to determine the first frequency point in each frame signal; wherein the noise estimation value of the first frequency point is less than the minimum power value; based on the number of the first frequency point at each frequency point sub-band of each frame signal, respectively determine whether noise mutation occurs at each frequency point sub-band of each frame signal; if it is determined that noise mutation occurs at the target frequency point sub-band of the target frame signal, the noise estimation value of the target frame signal at the target frequency point sub-band is updated to the power spectrum value of the target frame signal at the target frequency point sub-band. The application can accurately identify noise mutation and improve the updating efficiency of noise estimation.

This invention relates to the field of fan, speaker, and light design and control technology, and discloses a low-noise design method for a speaker fan based on fan noise. The method includes receiving the original audio signal, generating an audio power spectrum, and extracting low-frequency transient features; calculating the instantaneous masking threshold using a psychoacoustic model, and then inversely shaping the allowable noise power spectrum of the fan motor to generate a target fan spectrum; generating a fan drive signal based on the target spectrum using a random spread spectrum algorithm, and constructing an airflow velocity vector by combining the angular velocity fed back from the motor and the duct parameters; calculating the phase compensation amount based on the airflow velocity vector to generate a phase correction signal, and then combining the low-frequency transient features with an anti-phase aerodynamic impedance compensation component to synthesize a speaker signal; finally, driving the fan motor and speaker unit to operate synchronously. This invention utilizes the auditory masking effect to achieve invisible fan operation and cancels the interference of airflow on sound waves through flow field mapping and phase pre-distortion, achieving synergistic optimization of the sound field and airflow field.

A system and method of harmonizing computed tomography (CT) images to reduce variability introduced by differing reconstruction kernels. The method includes acquiring a CT image of a plurality of regions of a patient. The method includes calculating, by a processing device, a noise power spectrum (NPS) of a uniform region among the plurality of regions. The method includes selecting, from a library of reconstruction kernels, a first reconstruction kernel based on the NPS of the uniform region of the plurality of regions. The method includes generating a harmonized CT image based on the first reconstruction kernel and the CT image.

The invention discloses a low-voltage cable fault fixed-point detection method and system. The low-voltage cable fault fixed-point detection method comprises the steps that a space sensing array composed of a main sensor, a plurality of reference sensors and a load current sensor is deployed on a low-voltage cable, and synchronous sampling is carried out; constructing a noise base matrix based on the output of the reference sensor, and inhibiting the environmental noise and electromagnetic interference in the main sensor signal through adaptive weight filtering; carrying out frequency domain analysis on the de-noising signal, constructing a gain function in combination with an estimated noise power spectrum, and carrying out selective enhancement on a fault characteristic frequency band; performing time-domain correlation analysis on the enhanced electromagnetic signal and the load current signal, extracting cross-correlation parameters, time-domain statistical characteristics and frequency-domain characteristics, and fusing the cross-correlation parameters, the time-domain statistical characteristics and the frequency-domain characteristics into a multi-dimensional characteristic vector; and finally inputting a pre-trained fault diagnosis model, and outputting a fault type and positioning information. The method effectively improves the extraction and identification capability of weak fault signals in a complex electromagnetic environment, and achieves the precise recognition and fixed-point detection of the fault type of the low-voltage cable.