The principle of statistically optimal planar near-field acoustical holography and the sound field separation technique

Near-field acoustic holography (NAH) is a powerful technique for identifying noise sources and visualizing acoustic field.The theory and algorithm of NAH techniques are introduced , and it is proved by experiment and simulation. The researches on near field acoustical holography (NAH) are reviewed，including the sound field separation technique and Patch NAH technique arisen in recent years.The difficulties in NAH and research on current situations are discussed , Finally,some engineering applications are introduced by detailed examples.

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Sound field separation technique and its applications in near-field acoustic holography

Acta Physica Sinica ◽

10.7498/aps.54.789 ◽

2005 ◽

Vol 54 (2) ◽

pp. 789

Author(s):

Yu Fei ◽

Chen Jian ◽

Li Wei-Bing ◽

Chen Xin-Zhao

Keyword(s):

Near Field ◽

Sound Field ◽

Separation Technique ◽

Acoustic Holography ◽

Field Separation

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Sound field separation of multiple coherent sound sources with single measurement surface

Journal of Vibration and Control ◽

10.1177/10775463211020188 ◽

2021 ◽

pp. 107754632110201

Author(s):

Jin Mao ◽

Jinfu Du ◽

Kai Liu ◽

Jiang Liu ◽

Yahui Cui

Keyword(s):

Near Field ◽

Sound Field ◽

Single Measurement ◽

Sound Sources ◽

Equivalent Source ◽

Coherent Sources ◽

Measurement Surface ◽

Acoustical Holography ◽

Field Separation ◽

Source Number

Sound field separation based on near-field acoustical holography has been developed worldwide, but with the increase in the number of sound sources, traditional measurement methods and calculation methods will generate more workload. To reduce the number of measuring points and save calculation time, the sound field separation of multiple coherent sources with a single measurement surface is proposed. On the basis of separating two coherent sources with this method, the separation formula of more sources based on an equivalent source method is given. Through numerical simulation, the effects of the number of holographic surface measuring points, measuring distance, array shape, and equivalent source number on the calculation accuracy of the sound field separation were compared at different frequencies. The correctness and effectiveness of the sound field separation method with a single surface are verified by actual experiments.

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SOUND FIELD SEPARATION TECHNIQUE WITH SINLGE HOLOGRAPHIC PLANE AND ITS APPLICATION IN ACOUSTIC HOLOGRAPHY

Journal of Mechanical Engineering ◽

10.3901/jme.2004.02.112 ◽

2004 ◽

Vol 40 (02) ◽

pp. 112 ◽

Cited By ~ 1

Author(s):

Fei Yu

Keyword(s):

Sound Field ◽

Separation Technique ◽

Acoustic Holography ◽

Field Separation

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Reconstruction of Three-Dimensional Sound Field from Two-Dimensional Sound Field Using Optical Computerized Tomography and Near-Field Acoustical Holography

Japanese Journal of Applied Physics ◽

10.1143/jjap.48.07gc03 ◽

2009 ◽

Vol 48 (7) ◽

pp. 07GC03 ◽

Cited By ~ 4

Author(s):

Takeshi Ohbuchi ◽

Koichi Mizutani ◽

Naoto Wakatsuki ◽

Kojiro Nishimiya ◽

Hiroyuki Masuyama

Keyword(s):

Computerized Tomography ◽

Near Field ◽

Three Dimensional ◽

Sound Field ◽

Two Dimensional ◽

Acoustical Holography

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Simulation and experimental investigations for the patch near-field acoustical holography

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes727 ◽

2008 ◽

Vol 222 (6) ◽

pp. 945-953 ◽

Cited By ~ 1

Author(s):

C Yang ◽

J Chen ◽

J Q Li ◽

W F Xue

Keyword(s):

Fourier Transform ◽

Sound Pressure ◽

Near Field ◽

Sound Field ◽

Experimental Investigations ◽

Regularization Methods ◽

Aperture Size ◽

Measurement Surface ◽

Physical Necessity ◽

Acoustical Holography

In order to reconstruct the sound field, the fast Fourier transform (FFT)-based near-field acoustical holography (NAH) demands that the measurement surface must extend to a region where the sound pressure decreases to a low level. This method is unfit for reconstructing the partial sound field in which the measurement aperture size is limited either by physical necessity or as a way of reducing the measurement cost. Statistically optimal NAH (SONAH) performs plane-to-plane calculations directly in the spatial domain, avoids all errors occurred in the FFT-based NAH and significantly increases the accuracy of the reconstruction of the partial sound field. In the present work, combined with the different regularization methods, SONAH is performed for reconstructing the partial sound field. The errors over the central and the peripheral sections of the reconstruction area are researched separately. Simulations and experiments show that SONAH is successful in reconstructing the partial sound field and the errors over the central sections are smaller than that over the peripheral sections. Experiments demonstrate that Tikhonov regularization in conjunction with Engl's criterion is suitable for the reconstruction of the practical sound field.

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Near-field acoustical holography incorporating compressive sampling: Effect of measurement distance and array density

Noise Control Engineering Journal ◽

10.3397/1/376839 ◽

2020 ◽

Vol 68 (6) ◽

pp. 470-489

Author(s):

Tongyang Shi ◽

Weimin Thor ◽

J. Stuart Bolton

Keyword(s):

Sound Source ◽

Near Field ◽

Source Region ◽

Sampling Rate ◽

Sound Field ◽

Compressive Sampling ◽

Sound Power ◽

L1 Norm ◽

Measured Intensity ◽

Acoustical Holography

To identify sound source locations and strength by using near-field acoustical holography (NAH), many microphones are generally required in order to span the source region and to ensure a sufficiently high spatial sampling rate. It is often the case that hundreds of microphones are needed, so such measurements are costly, which has limited the application of NAH in industrial settings. Recently, however, it has been shown that it is possible to accurately identify concentrated sound sources with a limited number of microphones based on compressive sampling theory. Here, the theory of the four NAH methods that were studied in the present work, that is, statistically optimized near-field acoustical holography (SONAH), wideband acoustical holography (WBH), l1-norm minimization, and a hybrid compressive sampling method, is briefly reviewed. Note that the latter three procedures incorporate elements of compressive sampling. Then, a simulation with one monopole as the sound source was conducted to illustrate some basic characteristics of these algorithms. In the experimental portion of the work, a multi-element loudspeaker was used as the sound source. A near-field intensity scan was conducted to measure both the true intensity spatial distribution and the sound power generated by the loudspeaker to provide a basis against which the values obtained from the holography reconstructions could be compared. The sound field was reconstructed by using both near- and far-field measurements, and the number of microphone measurements used to reconstruct the sound field was systematically decreased by increasing the spacing between microphones. Both in the simulation and experiment, the sound field was reconstructed by using the four NAH methods mentioned above. Then, the reconstruction results were comparedwith the measured intensity results in terms of spatial localization and sound power, and the benefits of the compressive sampling approach are illustrated.

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