40 results about "Acoustical holography" patented technology

The invention belongs to the field of noise like sound field reconstruction and visualization, and particularly relates to a movable noise source recognizing method based on a local near field acoustical holography method. The movable noise source recognizing method includes the steps that sound pressure on a measuring plane H is measured; Doppler effect removal is carried out on the sound pressure obtained through measuring to obtain sound pressure, not containing the Doppler effect, on the measuring plane H; zero padding expansion is performed on the sound pressure on the measuring plane H to obtain sound pressure on a measuring plane H+; a transmission matrix between the sound pressure on the measuring plane H+ and the sound pressure on a reconstruction plane S is calculated; the sound pressure on the reconstruction plane S is solved. Based on the local near field acoustical holography method, the movable noise source recognizing method has the advantages of being simple in calculation, short in calculation time, high in calculation efficiency and the like compared with a traditional method.

The invention discloses a near-field acoustical holography method based on a combinatorial optimization regularization method. The sound pressure at each point measured on a holographic surface is used, based on a statistical optimal cylinder near-field acoustical holography method, the truncated singular value and standard Tikhonov combinatorial optimization regularization method are used for selected wave number vectors to suppress measurement errors of the wave number vectors caused by the noise and random errors, and that is the combinatorial optimization regularization method; by using the combinatorial optimization regularization method and a GCV method, a superposition coefficient matrix and the sound pressure at each point measured on the holographic surface are obtained, and a sound field on the surface of shell structure equipment can be obtained by expressing the sound pressure at each point on the surface of the shell structure equipment as linear superposition of the conformal measurement surface sound pressure; and effectiveness of the near-field acoustical holography method in shell radiation noise analysis is fully demonstrated, the near-field acoustical holographymethod is suitable for the cylindrical shell structure, a sound field of a cylindrical underwater vehicle is displayed visually, and thus the magnitude and distribution of a radiated sound field can be seen intuitively, so that important theoretical significance and engineering application values are achieved.

A three-dimensional array (10) of microphones (M) is used to determine the three-dimensional sound field above a surface element (ΔS) of a sound emitting surface (S), and the air-particle velocity (un) at the surface element (ΔS) is determined using Near-Field Acoustical Holography (NAH). A volume velocity sound source (11) is used to emit a volume velocity (Qv) in a listening position, and the array (10) of microphones (M) is used to determine the resulting three-dimensional sound field above the surface element (ΔS), and using NAH the resulting sound pressure at the surface element (ΔS) is determined. The acoustic transfer function (H) between the surface element (ΔS) and the listening position is assumed to be reciprocal and is determined as the ratio of the resulting sound pressure at the surface element (ΔS) to the volume velocity (Qv). The sound pressure in the listening position resulting from the surface element (ΔS) is determined as Δp=H.(un. ΔS).

The invention provides a near-field acoustical holography reconstruction method based on an equivalent source method. A radiated sound field of a vibration radiator is considered to be formed by a superposition of sound fields generated by a series of equivalent sources arranged in the radiator. Source intensity of the equivalent sources can be obtained by normal velocity matching of the radiator surface. Thus, sound radiation is calculated. The near-field acoustical holography reconstruction method based on the equivalent source method is suitable for near-field acoustical holography of sound sources of arbitrary shapes and is adopted to raise computational efficiency and computational accuracy.

The invention provides a near-field acoustical holography reconstruction method based on the Fourier transformation and source strength simulation technology. The near-field acoustical holography reconstruction method based on the Fourier transformation and source strength simulation technology comprises the steps that continuous simple sources are arranged on a rectangular virtual source surface, and a source strength function is a three-dimensional free space Green function; double Fourier series expansion is carried out on an unknown source strength density function, and a sound pressure expression is deduced; expressions of the sound pressure on measuring points on a holographic surface are deduced through quick Fourier transformation and inverse transformation calculation, and a non-homogeneous linear equation set which uses a Fourier series expansion coefficient as an unknown term and the sound pressure as a constant term is formed through arrangement; the Fourier series expansion coefficient is obtained by solving the non-homogeneous linear equation set through a generalized inverse matrix, the Fourier series expansion coefficient is substituted into a reconstruction formula in a back substitution mode, the expression of the sound pressure on any field point in a radiation field is obtained, and reconstruction and prediction of the whole space sound field are achieved. According to the near-field acoustical holography reconstruction method based on the Fourier transformation and source strength simulation technology, implementation is easy, the calculating speed is high, limitation cannot be caused by the limited hole diameter, and the near-field acoustical holography reconstruction method is applicable to sound sources with any shapes.

The present invention provides a reflective acoustic holographic imaging method based on a metasurface, including a reflective acoustic holographic imaging device. The method includes: acquiring the working frequency of the reflective acoustic holographic imaging device, determining the initial sound wave at the working frequency; Vertically incident into the reflective acoustic holographic imaging device to obtain the reflected sound wave; input the reflected sound wave to the reflected sound wave correction model to obtain the corrected sound wave; reconstruct the target image on the imaging surface of the reflective acoustic holographic imaging device according to the corrected sound wave; the present invention The beneficial effect is: it is used to solve the problem that the traditional use of acoustic metasurfaces to directly generate a holographic sound field by designing a unit structure will cause deviations in holographic imaging due to acoustic wave interference when applied in special scenes.

The invention provides a noise source identification method adopting vibration speed measurement and a partial near-field acoustical holography method.. The method comprises the following steps of: measuring the vibration speed of a normal mass point on a finite aperture measurement surface H positioned at a near field; performing zero-padding expansion on the vibration speed; calculating a transmission matrix between the measurement surface and a sound source surface; and finally calculating so as to obtain sound pressure on the sound source surface S and the vibration speed of the normal mass point. The vibration speed of the normal mass point is used as an input value for sound field reconstruction, so that sound field information with relatively high precision can be acquired. Compared with the conventional iterative partial near-field acoustical holography method, the method adopting the partial near-field acoustical holography method has the advantages of being simple in calculation operation, short in calculation time, high in calculation efficiency and the like and is used for identifying and positioning a noise source and reconstructing a sound field.

The invention discloses a system for detecting a non-stationary acoustic source based on a near-field acoustical holography technology. The system is characterized by sequentially comprising an acoustic emission sensor array, a broadband acoustic emission pre-amplifier, an AD converter, a DSP, an upper computer and a graphic displayer. Acoustic source recognition algorithm analysis and processing software is operated in the upper computer. The non-stationary acoustic source is positioned through the near-field acoustical 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 provides a piezoelectric underwater sound transducer acoustic radiation mode measurement method and system based on combination near-field acoustical holography. In the method, the combination near-field acoustical holography is utilized to reestablish sound field, sound pressure and radiation surface vibration velocity; on the basis of an acoustic radiation operator matrix obtained based on measurement data and with the sound field radiation theory being combined, the acoustic radiation power of a piezoelectric underwater sound transducer is expressed to be a positive definite quadric form; and positive definite and conjugate performance of the matrix are utilized to obtained an acoustic radiation mode of the structure. The system comprises a glass water tank, an industrial control computer with PXI bus, a transducer excitation module based on the PXI bus, a sound pressure and vibration velocity acquisition module and a three-dimensional motion platform. The method and system in the invention break the limitation that acoustic radiation mode in the current complex underwater structure can only be solved numerically, provide a new idea for research on the piezoelectric underwater sound transducer, and also provide basis for structure optimization of the piezoelectric underwater sound transducer.