Sound Field Separation Method and Experiment Based on Virtual Double Holographic Planes

Near-field acoustic holography is a cutting-edge sound field visualization technique that allows the acquisition of sound pressure amplitude and phase information in a region near a sound source to reconstruct the surface “acoustic highlights” of the sound source by means of area array, near-field measurements. Near-field acoustic holographic measurements in the free sound field, and the related algorithms to locate and identify noise sources, have many applications in engineering. However, there are still many problems to be studied for the accurate localization and identification of noise sources in non-free fields for large size underwater body sources. Firstly, the theoretical derivation of the sound field separation method based on the virtual double holographic planes is carried out. Secondly, to study the key parameters of the sound field separation method based on the virtual double holographic planes, the genetic algorithm is introduced to select the optimal number of expansion terms for the spherical waves, to give the regularized combination method, and to perform simulations. Then, the simulation studies of air acoustic field and water acoustic field in complex environment are conducted for the sound field separation method based on virtual double holographic planes, and to discuss the effects of measurement parameters on the sound field separation errors. Finally, the feasibility and effectiveness of the sound field separation method based on the virtual double holographic planes are verified in the hydroacoustic tests. Moreover, the reconstruction error in the test is analyzed and a method to reduce the error is given. The results show that the sound field separation method based on virtual dual holographic planes only needs to measure the sound pressure value of a single holographic plane, and there is no requirement for the shape of the holographic plane. This method has the advantages of simple sound field testing, no requirement for the measurement array, and high accuracy of sound field separation compared with the traditional sound field separation method.