63 results about "Acoustic holography" patented technology

The invention discloses a fault detecting device of near field acoustic holography sound image mode identification and a detecting method thereof in the field of industrial detection. The device comprises a microphone array, a scanner frame, a reference source, a clamped rib plate, an excitation source and a data acquiring system. The invention adopts sound pressure amplitude and distribution changes under mechanical normal and fault states, borrows ideas from applications of an image diagnosis technology in other fields and utilizes image processing, feature extracting and mode identifying technologies to process a near field acoustic holography image. Experiments show that the method is effective, vibration source positioning and identifying functions coordinated with the holographic imaging technology is proven, the image feather extracting and mode identifying technologies are combined with the acoustic imaging technology, thus broadening the application range of the acoustic imaging technology and bringing a set of effective acoustic fault diagnosis technologies and feasibility of being widely used in engineering thereof.

The invention provides statistically optimal near-field acoustical holography used for visual recognition of air-conditioner noise sources and an operation method thereof. The operation method comprises the followings: determining the positions, frequency characteristics and distribution ranges of the noise sources, and distance between microphones on microphone arrays, number, sample rates and number of sampling points of microphones; calibrating arrayed microphones; collecting data; recording sound pressure data; processing the sound pressure data; reading the processed data and finally entering noise source recognition procedures. By the invention, complex sound pressure on reconstructive surfaces and vibration velocity of surface particles can be calculated directly via linear superposition of the complex sound pressure on a holographic plane in a spatial domain, thus essentially overcoming window effects and wraparound errors existing in near-field acoustical holography and avoiding the problems brought about by the demand of a large number of microphones by near-field acoustical holography, such as low reconstruction efficiency of sound fields and costly cost of measuring systems, etc. The invention is characterized by small number of demanded microphones, low measuring cost and high reconstruction efficiency of the sound fields.

The invention discloses a high-precision near-field acoustic holography algorithm adopting a weighted iteration equivalent source method, which is characterized in that a holographic plane H is arranged in a sound source near-field radiation area, and sound pressure PH on the holographic plane H is measured; an equivalent source plane Se is arranged at the side, which is away from the holographic plane H, of an object reconstruction plane T, and equivalent sources are arranged on the equivalent source plane Se; a relation between the sound pressure PH and each equivalent source is established by using a sound pressure transfer matrix between the equivalent source and the holographic plane H; and the source intensity Q of each equivalent source is solved by adopting a new iterative regularization algorithm with a posteriori weighted norm constraint penalty term, and then sound field data on the object reconstruction plane T is calculated by using the solved source intensity Q and the transfer matrix between the equivalent source and the object reconstruction plane T. According to the invention, the source intensity of each equivalent source is precisely solved by using the new iterative regularization algorithm with the posteriori weighted norm constraint penalty term, thereby avoiding source intensity energy leakage caused by a 2-norm penalty term in the Tikhonov regularization process. Compared with conventional equivalent source based near-field acoustic holography, a calculation result acquired by the method disclosed by the invention is more accurate.

A high spatial resolution phase-sensitive technique employs a near field ultrasonic holography methodology for imaging elastic as well as viscoelastic variations across a sample surface. Near field ultrasonic holography (NFUH) uses a near-field approach to measure time-resolved variations in ultrasonic oscillations at a sample surface. As such, it overcomes the spatial resolution limitations of conventional phase-resolved acoustic microscopy (i.e. holography) by eliminating the need for far-field acoustic lenses.

The invention discloses a pressure speed method sound field separation method, a measured sound field is provided with a measuring surface S; a sound pressure sensor is adopted to measure the sound pressure on the measuring surface S, and a particle velocity sensor or a sound intensity probe is adopted to measure the particle speed on the measuring surface S; both sides of the measuring surface S are provided with the imaginary source surfaces S1 <*> and S2 <*> which are provided with the equivalent sources; the transfer relationship between the equivalent sources and the sound pressure and the particle speed on the measuring surface S is constructed; the separation of sound source radiation sound pressure and the particle speed of both sides on the measuring surface according to the transfer relationship is realized; the sound field separation is realized by measuring the speed relation of sound pressure and particle on each surface; and the equivalent source method is adopted as the sound field separation arithmetic, the calculation stability is good, the calculation precision is high, and the implement is simple. The method can be widely applicable to the near-field acoustic holography measurement in the environments of internal sound field or noisy sound, the sound intensity method sound source identification in the noisy environment, the material reflection coefficient measurement, and the separation of the scattering sound field.

The present invention relates generally to a method of visualizing the sound fields of sound sources using acoustic holography, which discriminates the sound fields of individual sound sources having the same frequency component and visualizes the sound fields thereof.In the method, sound pressures are calculated on a sound source plane using sound pressures measured on a hologram plane. A single sound source having a position of a maximum sound pressure on the sound source plane is extracted, and a value of the sound pressure at the position is evaluated as a signal coherent to the sound source. A sound field of the extracted sound source is obtained using the coherent signal. The sound field is eliminated from sound fields of all sound sources, and it is determined whether any remaining sound field exists. The process returns to the sound field obtaining operation if any remaining sound field exists.

The invention relates to a diagnostic system of a non-contact type rotary mechanical failure in the technical field of detection, comprising a sound pressure measurement device, a computer, a sound field reconstructing module, an acoustic holography training sample storage module, an acoustic holography test sample storage module, an off-line training module and an online diagnostic module, wherein the sound pressure measurement device is connected with the computer, the computer is connected with the sound field reconstructing module, the sound field reconstructing module is connected with the acoustic holography training sample storage module and the acoustic holography test sample storage module, the acoustic holography training sample storage module is connected with the off-line training module, the acoustic holography test sample storage module is connected with the online diagnostic module, the off-line training module is connected with the online diagnostic module, the acoustic holography training sample storage module and the acoustic holography test sample storage module are connected with the computer, and the acoustic holography training sample storage module is connected with the online diagnostic module. The invention is a non-contact type, has simplicity and high accuracy rate and obtains favorable online diagnostic effect through optimization.

A system and method for analyzing a sample is described. The system may include, for example, a light source and a scanning probe microscope probe. The light source may generate a coherent laser beam that is modulated by a waveform of a lower frequency. The modulated laser beam is absorbed by the sample causing thermally induced expansion and resulting in an excitation of acoustic waves. The probe is locally deployed near the sample and detects, in real time, perturbations in the excited acoustic waves to detect surface and buried structures of the sample.

The invention discloses a metamaterial capable of realizing acoustic holography based on phase amplitude modulation. The metamaterial includes a substrate, n*m substrate-penetrating units are arranged on the substrate, n represents n columns and is a positive integer, m represents m rows and is a positive integer, each unit includes a first external channel, a middle channel, and a second external channel that are coaxial, the cross sections of the first external channel, the middle channel, and the second external channel are square in shape, the edge length of the cross sections of the first external channel and the second external channel is lambda / 5, the edge length of the cross section of the middle external channel is in the range of 0-lambda / 5, the thickness of the substrate is lambda, the height of the first external channel is in the range of lambda / 10-3lambda / 5, and the lambda represents the wavelength of the incident sound wave. According to the invention, the inner radius of the middle channel changes in the range of 0-lambda / 5 to realize different reflection amplitude, the position of the middle channel is changed to realize different reflection phase, and meanwhile, the wave phase and amplitude can be modulated for acoustic holography imaging.

Systems and methods of detecting and identifying a leak from a container or building. Acoustic pressure and velocity are measured. Acoustic properties are acquired from the measured values. The acoustic properties are converted to infiltration / leakage information. Nearfield Acoustic Holography (NAH) may be one method to detect the leakages from a container by locating the noise sources.

The invention discloses an indoor noise source localization method based on spherical surface near-field acoustic holography reconstructing reactive sound intensity. The method comprises the followingsteps: (1) calculating a three-dimensional spatial sound field data radiated by a mechanical sound source inside a regular small room; (2) using a spherical microphone array with Q array elements toacquire a sound pressure signal radiated from the target sound source to the three-dimensional space; (3) subjecting the Q pieces of microphone data of the spherical array and the first microphone data to cross spectrum analysis separately to obtain the frequency-domain complex sound pressure of the entire spherical array; (4) using a spherical near-field acoustic holographic algorithm to reconstruct the sound pressure and the mass point vibration velocity of the sound source surface; and (5) using the complex sound pressure and the mass point vibration velocity to reconstruct the surface complex sound intensity near the sound source to extract the reactive sound intensity; and determining the location of the indoor noise source by the reactive sound intensity distribution. Compared with the prior art, the method utilizes a fact that the reactive sound intensity is powerful in the near-field region of the sound source to eliminate the influence of indoor reverberation environment and effectively locate the indoor noise source.

The invention discloses a statistical nearfield acoustic holography method for a conical surface sound source. A measurement surface conformal with shell structure equipment is used for obtaining holography sound pressure data. On the basis of a statistical optimal cylindrical surface nearfield acoustic holography theory method, through cylindrical surface-conical surface coordinate transformation, a conical shell structure equipment radiation sound field is calculated directly through compound sound pressure on a spatial domain holography surface, the application blank of the nearfield acoustic holography technology in the conical surface sound source is filled up, the effectiveness of the nearfield acoustic holography technology in low-frequency noise analysis is displayed, the nearfieldacoustic holography technology is suitable for an underwater ordnance of a tapered shell structure so as to provide a theoretical basis for the acoustical stealth performance evaluation of the equipment of the tapered shell structure, and therefore, the nearfield acoustic holography method has important theoretical significance and an engineering application value. The statistical nearfield acoustic holography method is suitable for the radiation sound field reconstruction of the equipment of the tapered shell structure mainly under low-frequency vibration noise, the radiation sound field ofthe equipment of the tapered shell structure is visually displayed so as to visually see the size and the distribution situation of the radiation sound field.

The invention relates to a non-conformal measurement near field acoustic holography sound field rebuilding method, and relates to the technical field of acoustics. The method includes the steps that spherical wave function q(x,y) in a common wave superposition method (see the formula in the description) is replaced by a compound ray wave function with principal value directivity, by means of the method, when the holographic plane and a sound source shape are under the non-conformal condition, namely a planar array, a spherical array, a cylindrical surface array and other regular shape arrays are adopted in a holographic measurement plane, and a sound source is in an any shape, a system matrix is still in the good state of main diagonal domination, magnitude equivalence and approximate symmetry, numerical value inversion can be directly conducted on the system matrix efficiently and accurately, approximate solutions of ill-posedness problems can be obtained without using a regularization method or using the regularization method less, some variables of virtual equivalent sources are analyzed and prolongated to a complex space from a traditional real space, appropriate virtual damp is added, and therefore unique solution is obtained in the full wave number field.

The invention discloses a full-frequency-domain identification method for a vibration noise source of a transformer, and relates to a noise source identification method. The method comprises the following steps that sound pressure signals of the vibration noise source of the transformer are collected and measured, and divided according to the frequency domain; an acoustic holography method is usedto reconstruct low-frequency signals and calculate the vibration speed in the normal direction of low-frequency noise; a wave beam formation method is used to reconstruct high-frequency signals and calculate the vibration speed in the normal direction of high-frequency noise; and the noise sound pressure signals in the full frequency domain and the vibration speed in the normal direction of noisein the full frequency domain are calculated to identify full-frequency-domain noise of the vibration noise source of the transformer. Wave-number-domain zero-fill extrapolation is carried out on low-frequency sound pressure signals obtained by measuring an acoustic holographic measurement side, a result after zero-fill extrapolation is used to carry out reconstruction, reeling errors and an edgeGibbs effect caused by large size of the transformer are overcome, and noise of the vibration noise source of the transformer is identified in the full frequency domain.

The invention discloses a case equipment surface acoustic field reconstruction method based on statistical optimal near field acoustic holography. A measuring surface conformal with the case structureequipment is used to acquire holographic acoustic pressure, the surface acoustic field of the case structure equipment is calculated through the linear superposition of the complex acoustic pressureon the holographic surface of the spatial domain by using a statistical optimal column surface near field acoustic holography theory algorithm, and the window effect and the winding error in the nearfield acoustic holography are fundamentally solved. The method has the advantages of less number of microphones, low measurement cost, high acoustic field reconstruction efficiency, high precision andthe like. According to the method, the accurate reconstruction of the surface acoustic field of the column and column similar case structure equipment is realized, the method can be applied to underwater weapons such as a submarine, the reconstruction precision and the efficiency of the surface acoustic field of the case structure equipment can be effectively improved, the theoretical basis is provided for the acoustic stealth performance evaluation of the case structural equipment, which has important theoretical significance and engineering application value.

The invention relates to a system and method for detecting plant diseases based on near field acoustic holography technology. According to acoustic emission phenomena of plants and on the theoretical basis of the near field acoustic holography technology of a distributed source boundary point method, a cylindrical surface-spherical surface non-conformal-surface acoustic holography experiment model is established, and simulation experiments on single sound sources and double sound sources are respectively carried out. By changing of parameters, in the model, such as the holographic cylindrical surface radius, holographic measuring point number, and node number on reconstruction spherical surface, distance between fictive particular solution sources and nodes on the reconstruction spherical surface, and the like, feasible experimental parameters are obtained. Simulation results show that the method can accurately identify and locate the position of an acoustic emission source. On the basis of the experimental parameters, a signal acquisition acoustic holography experiment system which adopts DSP as a core is established, and data analysis and processing are carried out by an upper computer which adopts Labview as a software platform. The system and method for detecting plant diseases based on the near field acoustic holography technology adopt plant acoustic emission signals as important sensitive information to know the growth states and disease-affected situations of the plants, and through studies of the acoustic emission signals based on the near field acoustic holography technology of the distributed source boundary point method, the diseases can be timely discovered and identified, and a new way and the new method for the prevention and control and detection of the plant diseases is provided.

The invention provides a near-field acoustic holography fast algorithm based on complex ray wave superposition, and relates to the technical field of acoustics. The method comprises the following steps: 1) selecting the shape of holographic and virtual equivalent source surfaces; 2) constructing a complex ray wave superposition method through a ray wave function; 3) solving expansion of an unknown source strong density function Fourier; and 4) reestablishing complex sound pressure and vibration velocity of a sound field. The method can overcome problems in the prior art under a non-conformal measurement condition, can not only enable calculation accuracy to be very high, but also enable solution to be unique; and meanwhile, fastness is achieved.

The invention discloses a finite space plane near-field acoustic holography measurement method based on spatial Fourier transform, which comprises the following steps: 1, establishing a free field andfinite space radiation sound field model based on a point sound source, and extracting complex sound pressure of a point sound source reconstruction surface in the free field and complex sound pressure data on a holographic surface in a finite space; 2, calculating a sound pressure angle spectrum of a point source reconstruction surface in a free field and a point source holographic surface in afinite space, and calculating a transfer operator G-1 of the reconstruction surface and the holographic surface; 3, measuring to obtain complex sound pressure data on the holographic surface with thereconstructed sound source in the limited space; and calculating a holographic surface sound pressure angle spectrum; 4, multiplying the holographic surface sound pressure angle spectrum in the step 3by the transfer operator G-1 in the step 2 to obtain a sound pressure angle spectrum on the reconstruction surface; and 5, performing wave number domain windowing on the sound pressure angle spectrumof the reconstruction surface; and performing Fourier inverse transformation on the windowed reconstructed sound pressure angular spectrum to obtain reconstructed surface sound pressure. According tothe method, the finite space test environment is considered, and the reconstruction precision is improved by solving the transfer operator in the free field and the finite space.

A near-field acoustic holographic calibration and measurement method for an impedance characteristic of a planar sonar array belongs to the technical field of research on the near-field acoustic holographic measurement method for the impedance characteristic of large planar emission arrays. The method is characterized by including an impedance characteristic calculation method of the planar emission array; a radiation impedance calibration method based on near-field acoustic holography; a BAHIM method based near-field acoustic holographic transformation method and algorithm; value simulation via a radiation impedance calibration method based on near-field acoustic holography; and establishment of a near-field acoustic holographic theoretical test model for the impedance characteristic of alow-frequency planar sonar array. Acoustic characteristic calibration demands of an active sonar device can be monitored according to water sound, research on basic principles of near-field acousticholographic calibration for the impedance characteristic of the planar sonar array, design of a near-field acoustic holographic calibration scheme, development of impedance calibration software of thelow-frequency sonar array, and near-field acoustic holographic calibration and measurement test can be implemented in a targeted way, and thus, the calibration capability of a low-frequency emissionenergy transducer calibration system can be improved, and problems in evaluating the impedance characteristic of the low frequency sonar are solved.

A method and system for predicting acoustic fields based on generalized moving frame acoustic holography are disclosed. The method includes acquiring a first wavenumber spectrum on a measurement plane according to a moving coordinate system, converting the first wavenumber spectrum to a second wavenumber spectrum on a reference coordinate system using a relative velocity between the measurement plane and a medium, converting the second wavenumber spectrum to a third wavenumber spectrum on a prediction plane using an acoustic wave propagation theory, converting the third wavenumber spectrum to a fourth wavenumber spectrum on a moving coordinate system using a relative velocity between the medium and the prediction plane, and computing acoustic fields on the prediction plane using the fourth wavenumber spectrum.

The invention provides a near-field acoustic holography test method based on a spherical function basic solution and a near-field acoustic holography test device thereof. The test method comprises the steps that the order N of the used spherical function basic solution and the number and the position of microphones on a spherical holographic measuring surface are determined, sound pressure measurement is performed on the determined measurement points and the acoustic physical quantity of the surface of a vibration structure is reversely reconstructed by using the acquired measurement result. The device comprises a base (1), a rotating shaft (2), a semicircular support (3) and a test mechanism (4). The semicircular support (3) can circumferentially rotate along with the rotating shaft (2). The test mechanism (4) is fixedly installed on the semicircular support (3) and can measure acoustic pressure information of the spherical holographic measuring surface surrounding the vibration structure (5).

The invention discloses a method for detecting non-stationary acoustic sources based on a near-field acoustical holography technology. The method includes the following steps that (1), according to the acoustic emission phenomenon of the non-stationary acoustic sources, a cylindrical surface-spherical surface non-conformal surface acoustical holography experimental model is established according to the near-field acoustical holography technology; (2), the number of detection points and the number of reconstructed spherical surface nodes are set for single acoustic sources on the experimental model, simulation experiment analyzing is performed, and parameters are selected; (3), according to the parameter selection result of single acoustic source simulation, double acoustic sources are reconstructed, and the effectiveness of the method is verified; (4), through analyzing experimental data, the selection rule of the distances from a particular solution point source to the nodes on a reconstructed spherical surface and main parameters affecting reconstruction precision are fictional; (5), according to optimal simulation experiment parameters, an acoustical holography experiment system is designed. The non-stationary acoustic source is positioned through the near-field acoustic holography technology, the position and the characteristics of the non-stationary acoustic source can be accurately measured, and therefore convenience is provided for effective control over noise.

The invention discloses an intelligent control system of a free sound field small acoustic holography measurement and inversion device. The invention relates to an automatic control system. The intelligent control system comprises a control center module and an accessory module, an upper computer interface module, an information input display module, a range finding module, a sound pressure test and acoustic inversion calculation module, a whole device horizontal adjustment driving module, a microphone array vertical motion driving module, a microphone array rotation motion driving module, a microphone array transverse motion driving module, a microphone array longitudinal motion driving module, a microphone array correction motion driving module and a sensor signal input module connectedwith the control center module. By means of the control system, the testing and inverting device can be automatically adjusted, coordinate positioning of the testing device can be automatically conducted, the sound pressure can be automatically tested, the sound pressure can be automatically calculated, the sound field can be inverted, and the control system has the advantages of being high in testing speed, high in data calculation precision, labor-saving and time-saving.

The invention belongs to the field of sound source positioning, and particularly relates to an aerodynamic noise source positioning method and system based on near-field acoustic holography. The aerodynamic noise source positioning method comprises the following steps: (S1) acquiring holographic surface sound pressure data through a microphone array; (2) eliminating the effect of a shearing layerfrom two aspects of a propagation path and amplitude, and correcting the holographic surface sound pressure data to obtain corrected holographic data; (3) processing the holographic data by adopting anear-field acoustic holography method, and reconstructing sound field data; and (4) inputting the reconstructed sound field data into a display, and displaying the sound source position. The invention further provides an aerodynamic noise source positioning system based on near-field acoustic holography. The aerodynamic noise source positioning system comprises a front-end subsystem, a rear-end subsystem and an optical fiber data transmission module. According to the invention, the insufficiency of the measurement area of the holographic surface in the jet flow and the disturbance to the airflow are avoided, the sound field image with high spatial resolution can be obtained, and the rapid and accurate positioning of the aerodynamic noise source is realized.

The invention provides an acoustic supersurface capable of simultaneously adjusting and controlling amplitude and phase. The acoustic supersurface comprises a plurality of structural units; a plurality of structural units is arranged in parallel in a same plane, and when arranged, a plurality of structural units is connected to each other as an integral body; the structural unit comprises: a solidpart and a hollow part; the solid part is internally provided with a folding channel, and the hollow part is hollow along an axial direction; the folding channel is composed of a starting section, anintermediate section and a tail section; the starting section is an inlet connecting channel, and the intermediate section is a square wave channel composed of a plurality of rectangular frames for connecting the intermediate section and the outside; and the inlet connecting passage and an outlet connecting passage are respectively located at the center positions of a rear end surface and a frontend surface of the solid part. The acoustic supersurface has the beneficial effects that the acoustic supersurface proposed by the invention can simultaneously control the amplitude and phase of theemitted acoustic wave in a full range, and can be used for acoustic holography and acoustic phantom, the variation parameters are small, the variation law is obvious, and the acoustic supersurface hasthe high industrial application value.

A method of determining a property of a sound field from a plurality of measured sound field parameters, the method comprising: receiving a plurality of measured sound field parameters each indicative of a sound field parameter measured by a sensor of an array of sensors, the sensor being positioned at a measurement position; providing a model of a sound field, the model comprising a set of elementary waves and having associated with it a set of model parameters; computing, from the model, computed values of the sound field parameter at each of the measurement positions and as a function of said model parameters; determining a set of parameter values of the model parameters so as to reduce an error measure by performing an iterative minimization process including a plurality of iterations, the error measure comprising an error term operable to compare the computed and the measured sound field parameters; computing the property of the sound field from the determined set of model parameters.

The invention discloses noise detection and noise reduction methods for a vehicle fuel cell engine system. The detection method comprises the following steps of S1, carrying out a noise source identification test on a vehicle through a near field acoustic holography method, after an A weighted sound pressure level distribution diagram of noise at different positions of the vehicle is obtained, analyzing an average sound pressure level frequency spectrum to obtain a peak frequency of the noise, and computing to obtain a sound pressure level at the corresponding frequency; S2, further identifying a noise source and a vibration source through a near field vibration noise test for a position corresponding to the sound pressure level larger than a first preset sound pressure level threshold value; and S3, performing hammering test on a plate of an accessory at the position corresponding to the first preset sound pressure level threshold value under a vehicle acceleration test working condition in order to determine the influence of noise resonance. The noise reduction method comprises a step of adopting a sound absorption material and / or changing the internal structure and the weight ofthe noise source. By the adoption of the methods, reliability and durability of an engine system under a vehicle-mounted condition are improved, and the acoustic shock noise of the vehicle is improved.

The invention aims at providing a sound field separation method based on a least square method of a Helmholtz equation. The sound field separation method comprises the following steps: acquiring a sound pressure on a measurement surface; resampling the sound pressure on the measurement surface to obtain different measuring point groups; decomposing the sound pressures generated by a sound source Aand a sound source B at each measuring point according to a sound pressure expansion formula in an HELS acoustic holography method, and establishing a transmission relationship between the sound pressures of the two sound sources on the measurement surface; establishing a transfer matrix between the measurement surface and the sound source surface; and performing singular value decomposition on the transfer matrix to obtain the sound pressure generated by the sound source A on the measurement surface or any position, thereby realizing sound field separation. According to the invention, the single measurement surface and the HELS method are used for sound field separation and reconstructionand only the sound pressure data of the single measurement surface need to be collected, so that thecollection workload and the collection cost are reduced; the number of needed measurement points is small, the calculation efficiency is high, and the implementation mode is simple.