30 results about "Time frequency filtering" patented technology

The present invention relates to a light-weight, small and portable ambulatory sensor for measuring and monitoring a person's physical activity. Based on these measurements and computations, the invented system quantifies the subject's physical activity, quantifies the subject's gait, determines his or her risk of falling, and automatically detects falls. The invention combines the features of portability, high autonomy, and real-time computational capacity. High autonomy is achieved by using only accelerometers, which have low power consumption rates as compared with gyroscope-based systems. Accelerometer measurements, however, contain significant amounts of noise, which must be removed before further analysis. The invention therefore uses novel time-frequency filters to denoise the measurements, and in conjunction with biomechanical models of human movement, perform the requisite computations, which may also be done in real time.

A method of reducing noise in an audio signal, comprising the steps of: using a furrow filter to select spectral components that are narrow in frequency but relatively broad in time; using a bar filter to select spectral components that are broad in frequency but relatively narrow in time; analyzing the relative energy distribution between the output of the furrow and bar filters to determine the optimal proportion of spectral components for the output signal; and reconstructing the audio signal to generate the output signal. A second pair of time-frequency filters may be used to further improve intelligibility of the output signal. The temporal relationship between the furrow filter output and the bar filter output may be monitored so that the fricative components are allowed primarily at boundaries between intervals with no voiced signal present and intervals with voice components. A noise reduction system for an audio signal.

In accordance with an embodiment, a method of generating an encoded audio signal, the method includes estimating a time-frequency energy of an input audio signal from a time-frequency filter bank, computing a global variance of the time-frequency energy, determining a post-processing method according to the global variance, and transmitting an encoded representation of the input audio signal along with an indication of the determined post-processing method.

The invention discloses a time-varying mixed-phase seismic wavelet extraction method based on time-frequency spectrum simulation, which is characterized in that: on the basis of generalized S-transformation improved on non-stationary seismic records, a time-frequency filter is introduced for the first time to the seismic records The time-frequency spectrum is filtered, and then the spectrum simulation method is used to estimate the wavelet amplitude spectrum at each moment. Under the assumption that the wavelet phase is time-invariant, the high-order cumulant bispectral method is used to remove the time-varying wavelet amplitude spectrum. The mixed phase spectrum of the wavelet is reconstructed from the seismic record, and finally the amplitude spectrum and the phase spectrum are combined to realize the extraction of the time-varying mixed phase wavelet. Compared with the conventional segmentation extraction method, the time-varying wavelet extraction method proposed by the present invention does not require the assumption that the wavelet is segmentally stable, and can accurately estimate the time-varying wavelet when there is a large change in the wavelet properties of adjacent layers , and the extraction of mixed phase of wavelet is more in line with the actual situation, it can analyze and process seismic data more finely and accurately, and has good application value in improving the resolution of seismic data.

The invention relates to a self-adaptive grid construction method and device used for bandwidth extended coding. The method comprises the steps of: S1, based on transient property analysis of input monophonic audio signals, carrying out frequency resolution selection, carrying out self-adaptive multi-resolution filtering on the input monophonic audio signals, and obtaining an optimum time frequency filtering signal; and S2, carrying out transient detection and positioning on each sub-band signal output after the filtering, carrying out self-adaptive grid construction respectively in a frequency direction and a time direction according to the transient property analysis of each sub-band signal and by considering set high frequency band code rates and ear critical frequency band characteristics, and obtaining an optimum time frequency grid under a current code rate. The invention further relates to bandwidth extended coding and decoding methods based on the method. According to the invention, based on audio signal characteristics and high frequency signal available code rate limits, multi-resolution filtering and self-adaptive time frequency grid construction are carried out, and the coding efficiency of high frequency parts of digital audio signals and the sound quality of the high frequency part signals are obviously improved.

The invention discloses a method for denoising a geophysical signal. The method herein includes the following steps: 1. conducting S transformation on an original geophysical signal, obtaining the time-frequency spectrum of the original geophysical signal; 2. conducting time frequency filtering on the time-frequency spectrum; 3. conducting threshold filtering on the signal after the time frequencyfiltering; 4. conducting s inverse transformation on the result from the threshold filtering, obtaining an initial denoised signal; 5. conducting empirical mode decomposition on the initial denoisedsignal, obtaining a plurality of intrinsic mode function components of the initial denoised signal; 6. conducting hilbert transformation and spectrum analysis on all the intrinsic mode function components of the initial denoised signal, selecting an intrinsic mode function which is associated with the original geophysical signal; and 7. reconstructing a signal by using the intrinsic mode function,obtaining the required denoised signal. According to the invention, the method herein can efficiently denoise the geophysical signal.

The invention provides an adaptive decomposition method generating filters based on the image segmentation technology. The method comprises the steps of firstly performing time-frequency transformation on to-be-analyzed signals to obtain corresponding time-frequency coefficients and time-frequency planes; secondly, performing threshold segmentation on the time-frequency planes to obtain binaryzation images; thirdly, marking connected domains in the binaryzation images; fourthly, generating a group of time-frequency filters according to the connected domains, performing filtering on time-frequency systems based on the time-frequency filters and outputting filtering results; fifthly, performing time-frequency inverse transformation on the filtering results to obtain decomposition results. When the sampling time of each frequency component of a to-be-decomposed signal is long enough, the method can have any frequency resolution; compared with the frequently-used empirical mode decomposition algorithm, the method increases the frequency resolution greatly, can perform adaptive decomposition on the signals with dense distribution of frequencies, and thus can calculate the instantaneous frequency and the instantaneous amplitude of each component, so that the application range of the adaptive decomposition algorithm is widened.

The invention relates to a receiving method of double-scattering signal components in a lattice multi-carrier parallel transmission system. According to the method, a new time-frequency filter group is constructed on inverse lattices corresponding to time-frequency lattices which send signals, so that the receiving of signal scattering components can be realized; by means of compactness simplification, signal scattering component receiving under a fast moving environment can be completed quickly; and therefore, the problem of the loss of information of a part of signal scattering components which is caused by the incompleteness of a filter group existing in a traditional receiver can be solved fundamentally, and compression redundancy and decoding performance can be both improved to a greater extent. With the receiving method of the invention adopted, defects in the receiving and processing of lattice orthogonal frequency division multiplexing (LOFDM) multi-carrier signals can be eliminated; the reliability of lattice multi-carrier data parallel transmission under the fast moving environment can be improved significantly; and the novel receiving of the lattice orthogonal frequency division multiplexing (LOFDM) multi-carrier signals can be realized; and based on parameter configuration adjustment, the receiving method can be used for a traditional multi-carrier system so as to improve the receiving performance of the traditional multi-carrier system.