Rectangular transducer is widely used in industrial non-destructive testing. Current studies generally assume that there is no attenuation in the medium. In this paper, the distribution characteristics of the radiated sound field in attenuation media of a rectangular transducer are theoretically calculated. Firstly, considering the attenuation of the medium, the analytical expression of sound field distribution in The Fresnel region is derived under the condition of Fresnel approximation. Secondly, the distribution characteristics of sound pressure on the beam axis are discussed. Finally, the sound pressure distribution in the far field is calculated using the Fraunhofer approximation and compared with the case without attenuation. This study provides an important reference for the method and process design of using rectangular transducer to detect attenuation materials.
In aerospace, petroleum, special equipment and electric power industries, ultrasonic non-destructive testing technology is widely used. A large number of rectangular ultrasonic transducers are adopted, including the one dimensional linear phased array ultrasonic testing which is widely used, recently. So the sound field characteristics of the rectangular transducer is critical for these applications. Because of the small attenuation in the medium, we ignore the attenuation in the material. In this paper, the acoustic field characteristics of the rectangular transducer are discussed. Firstly, the coordinate system is established and the analytical solution of the acoustic field distribution of the rectangular transducer is derived in detail by using Rayleigh integral method with Fresnel approximation. Secondly, the distribution characteristics of sound pressure on the beam axis are discussed, and the length of the near field is calculated. Finally, the calculation of far-field sound pressure with the Fraunhofer approximation is carried out. And the relationship between directivity and probe parameters is discussed. The study of this paper provides important suggestions for the process design of ultrasonic inspection by using rectangular transducers.
KEYWORDS: Transducers, Near field, Acoustics, Ultrasonics, Optics manufacturing, Safety equipment, Signal attenuation, Precision optics, Near field optics
Generally, the surface vibration velocity amplitude of a conventional rectangular acoustic probe is the same. Because of strong interference, the radiated sound field in the near-field is extremely uneven, and radiation side lobes appears in the far field, which are not conducive to its application in ultrasonic technology. A rectangular acoustic transducer with Gaussian vibration velocity distribution on the acoustic radiation surface can reduce or avoid the near field of extreme inhomogeneity and far-field side-lobe. So it can be used in medical ultrasound diagnosis and industrial nondestructive testing and can obtain better effect. In this paper, the radiated sound field of a rectangular transducer with Gaussian distribution of surface vibration velocity is calculated, theoretically. The medium is isotropic without attenuation. The center of the rectangular transducer is assigned as the origin of coordinates. And the plane of the surface is as XOY surface. Then the coordinate system is established. Using Rayleigh integral method, the calculation of the radiation sound field is carried out. Discussion of the acoustic field distribution including on the beam axis and the far field is carried out. It is found that the sound field distribution on the beam axis is closely related to the parameters of the transducer surface. The oscillation of the sound pressure on the beam axis can be avoided by adjusting the parameters. There is no side lobe in the far field. The study of this paper can provide a theoretical suggestion for the application of Gaussian rectangular transducer.
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