174 results about "Spherical harmonics" patented technology

Techniques of making a recording of or transmitting a sound field from either multiple monaural or directional sound signals that reproduce through multiple discrete loud speakers a sound field with spatial harmonics that substantially exactly match those of the original sound field. Monaural sound sources are positioned during mastering to use contributions of all speaker channels in order to preserve the spatial harmonics. If a particular arrangement of speakers is different than what is assumed during mastering, the speaker signals are rematrixed at the home, theater or other sound reproduction location so that the spatial harmonics of the sound field reproduced by the different speaker arrangement match those of the original sound field. An alternative includes recording or transmitting directional microphone signals, or their spatial harmonic components, and then matrixing these signals at the sound reproduction location in a manner that takes into account the specific speaker arrangement. The techniques are described for both a two dimensional sound field and the more general three dimensional case, the latter based upon using spherical harmonics.

Soundfield signals as such e.g. Ambisonics carry a representation of a desired sound field. The Ambisonics format is based on spherical harmonic decomposition of the soundfield, and Higher Order Ambisonics uses spherical harmonics of at least 2nd order. However, commonly used loudspeaker setups are irregular and lead to problems in decoder design. A method for improved decoding an audio soundfield representation for audio playback comprises calculating a panning function using a geometrical method based on the positions of a plurality of loudspeakers and a plurality of source directions, calculating a mode matrix Ξ from the loudspeaker positions, calculating a pseudo-inverse mode matrix μ+ and decoding the audio soundfield representation. The decoding is based on a decode matrix that is obtained from the panning function and the pseudo-inverse mode matrix Ξ+.

A sound capture device comprises a symmetric microphone array that includes non-radially-oriented directional sensors (101). The device typically derives a spherical harmonic representation of the incident sound field, and affords higher signal-to-noise ratios and better directional fidelity than prior arrays, across a wide range of audio frequencies.

In some embodiments of the invention one or more sound characteristics, such as gain or frequency, of a given component of a spatial audio signal are modified in dependence on a relationship between a direction characteristic of the given component and a defined range of direction characteristics. A plurality of transforms. each relating to a different frequency range, is preferably used to modify the sound characteristics. In some embodiments, spatial audio in a format using a spherical harmonic representation of sound components is decoded by performing a transform on the spherical harmonic representation, in which the transform is based on a predefined speaker layout and a predefined rule. The predefined rule indicates a gain of each speaker, when reproducing sound incident from a given direction. In some embodiments, a plurality of matrix transforms is combined into a combined transform, and the combined transform is performed on an audio signal.

The invention discloses a multi-sound-source positioning method based on formation of a real value weight beam in a spherical harmonic domain. The multi-sound-source positioning method comprises the steps that a sound field model that unit amplitude plane waves enter a spherical microphone array is firstly established; then a spherical harmonic domain noise source signal model is constructed; spherical harmonic domain real value beam forming is carried out on noise source signals received by the spherical microphone array to obtain the beam in the spherical harmonic domain; an MVDR beam when the gain of the spherical microphone array is the maximum is constructed, and the optimal real value weight at the time is obtained; finally, the peak point of the square of the real value weight in the spherical harmonic domain is calculated, and the dimensional orientation maximum estimated value point of sound sources is extracted. According to the multi-sound-source positioning method based on formation of the real value weight beam in the spherical harmonic domain, the optimum real value weight in the spherical harmonic domain is obtained by utilizing the formation of the MVDR beam, the defects of large calculation amount and high calculation complexity of a traditional method are overcome, the calculation amount is obviously lowered, all-dimensional estimation of a free space is met, and the sound field is sampled more sufficiently.

The invention relates to a new face-iris combination identifying method-characteristic layer extraction and combination. A face-iris characteristic extraction layer combining system is established according to nerve network, evolution calculation and fuzzy theory. For structure design, full and local geometry topological structure is adopted. A particle-group optimizing arithmetic is utilized to optimize network control parameters. When the characteristics of the face and the iris image are extracted, techniques of a super-resolution image reinforcing arithmetic, an illumination compensating arithmetic based on improved spherical harmonic function, gesture estimation based on linear relevant filters, Candide model based on a three-dimensional face and expression analysis based on an ASM arithmetic, etc., are adopted to robustly extract the eigenvectors of the face and the iris, and a self-developed double face-iris collecting device is also adopted to collect images of the face and the iris image. The method not only can establish a new system which is provided with learning capability and can automatically choose optimal network topological structure and automatically regulate net control parameters, but also can overcome and reduce the bad impacts of factors of environment and physiology, etc., during the extraction process to the independent characteristics of the face and the iris, thus effectively enhancing the identifying rate of the face-iris combination identification and promoting the system performance based on the face-iris combination identification to develop towards practical, reliable and acceptable directions.

Spatial encoding in magnetic resonance imaging (MRI) techniques is achieved by sampling the signal as a function of time in the presence of magnetic field gradients, e.g., X, Y, and Z gradients. The gradient magnets have in the past been assumed to generate a linear gradient, and typical image reconstruction techniques have relied upon this assumption. However, to achieve high speed performance, gradient magnets often sacrifice linearity for speed. This non-linearity, in turn, results in distorted images, the distortion often being sufficiently large to compromise the usefulness of MRI images for stereotaxy or longitudinal studies, where precise volumetric information is required. The disclosure provides practical methods for correcting distorted images resulting from such non-linearity in the gradient fields, as well as distortions resulting from translational, rotational, and / or winding / design errors in the field generating devices. The methods employ spherical harmonic expansions of the gradient fields and fast Fourier transform techniques to provide well-corrected images without undue computational burdens.

The invention discloses a real-time ionosphere modeling and monitoring method based on a regional CORS (Continuous Operational Reference System). The method comprises the steps of: receiving originaldual-frequency observation data and a navigation message of a regional CORS station, rejecting a gross error, and then calculating a satellite position, an elevation angle and latitudes and longitudesof a puncture point; employing the Hatch filtering method and employing a carrier smooth pseudo-range observation value for differencing to obtain a TEC (Total Electron Contents) observation value without a geometric ionosphere; employing a spherical ion function to simulate the TEC distribution of the regional ionosphere, taking the model parameters and the satellite and the receiver differential code deviation as parameters to be estimated, constructing observation vectors by employing the observation data of all CORS stations of the single epoch to construct an observation equation; establishing a Kalman filter to perform real-time filtering processing for the parameters to be estimated, and separating from hardware delay to obtain an ionosphere TEC model; and finally, employing a model to calculate the grid point ionosphere delay, and storing and broadcasting the grid point ionosphere delay to regional users in a grid form. After an ionosphere product is obtained, a regional single-frequency PPP user location precision is obviously improved, and the dual-frequency PPP user convergence time is significantly improved.

The invention discloses an automatic implementation method for a high-uniformity magnet shim coil design. The method comprises the following steps of: measuring the magnetic field intensity distribution within a region range by utilizing a nuclear magnetic resonance probe, and fitting the first 10-order components of the magnetic field expanded according to spherical harmonics by utilizing a least square method so as to obtain the intensity value of the shimming quantity of each order; inputting a shimming intensity numerical value, selecting an algorithm, and then storing the shimming intensity numerical value and the algorithm; assigning the stored numerical value and algorithm to a shimming code module; loading a Radia three-dimensional electromagnetic field calculation packet into the shimming code module and carrying out optimal computation on the optimization model; optimizing the calculation result, calculating shim coil shape parameters, a coil three-dimensional structural drawing and an error iteration path by virtue of a linear programming method or a particle swarm optimization based on an analytical method; and manufacturing a shim coil according to the calculated specific coil shape parameters and coil three-dimensional topological structure. The method disclosed by the invention can be used for achieving the purposes of simplicity in operation and high precision.