Abstract
For the sound field reconstruction of large conical surfaces, current statistical optimal near-field acoustic holography (SONAH) methods have relatively poor applicability and low accuracy. To overcome this problem, conical SONAH based on cylindrical SONAH is proposed in this paper. Firstly, elementary cylindrical waves are transformed into those suitable for the radiated sound field of the conical surface through cylinder-cone coordinates transformation, which forms the matrix of characteristic elementary waves in the conical spatial domain. Secondly, the sound pressure is expressed as the superposition of those characteristic elementary waves, and the superposition coefficients are solved according to the principle of superposition of wave field. Finally, the reconstructed conical pressure is expressed as a linear superposition of the holographic conical pressure. Furthermore, to overcome ill-posed problems, a regularization method combining truncated singular value decomposition (TSVD) and Tikhonov regularization is proposed. Large singular values before the truncation point of TSVD are not processed and remaining small singular values representing high-frequency noise are modified by Tikhonov regularization. Numerical and experimental case studies are carried out to validate the effectiveness of the proposed conical SONAH and the combined regularization method, which can provide reliable evidence for noise monitoring and control of mechanical systems.
Highlights
Vibration and noise have a great influence on the accuracy of mechanical processing and reliability of electromechanical products, especially stealth and detection performance of underwater vehicles
The sound pressure is expressed as the superposition of this characteristic elementary wave
The reconstructed conical pressure is expressed as a linear superposition of the holographic conical pressure
Summary
Vibration and noise have a great influence on the accuracy of mechanical processing and reliability of electromechanical products, especially stealth and detection performance of underwater vehicles. Near-field acoustic holography (NAH) is applied to gain three-dimensional (3D) visualization of sound radiation based on measurements over a surface near the sound source, whose ability to reconstruct the evanescent wave components ensures a very high spatial resolution. Wall [27] combined an equivalent wave model (EWM) and SONAH for the reconstruction of near-field pressures in multisource environments with lower errors and fewer measurements, which was used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers and produced accurate field reconstructions for both inward and outward propagation [3] Most of these existing studies focused on planar sound sources, and only some focused on cylindrical sound sources. This study is intended to provide a reference for the engineering application of conical SONAH and can benefit vibration and noise monitoring, reduction, and control for mechanical systems
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