Chun-Duck Kim

Design of the Double Ultrasonic Transducer for Nonlinearity Measurement of Acoustic Waves

In this paper, we propose and design a new ultrasonic probe that can effectively measure both the fundamental and the second-harmonic waves simultaneously. The transducer consists of two bonded Pb(Zr, Ti)O3 (PZT) disks with the same properties and the same polarization, and a variable capacitor is connected to the electric terminals of one of the PZT disks for the simulation and experiment. It is shown that the second harmonic as well as the fundamental component can be efficiently received by controlling the capacitance. The result of the nonlinearity parameter B/A for ethanol measured using the double ultrasonic transducer shows good agreement with the reference value, and the B/A value for soybean is obtained.

Improvement of Calculation for Radiation Impedance of the Vibrators with Cylindrical Baffle

In order to determine the size of the vibrating surface of an individual element and the spaces among elements in a cylindrically arrayed ultrasonic transducer, enormous calculations for mutual- and self-radiation impedances should be accomplished within a limited time. However, the direct application of the equation of Greenspon and Sherman to such numerical calculations requires a very long time to obtain high accuracy. In this study, an effective calculation algorithm was investigated by introducing subintervals into the integration of the Greenspon and Shermans equation. As results, limits of subintervals improving computation time and accuracy were fitted as functions of the size of the vibrating surface of the element and the size of the baffle.

Radiation Characteristics Improvement of Flexural Type Vibrator for Parametric Sound Source in Air

Generally, the phase difference between center and edge in a flexural type vibrator leads to high side-lobe levels when the vibrator is used in a parametric source. To decrease the side-lobe level, an arrayed method is investigated in which the vibrators are arrayed at an angle to the array surface. To analyze the radiation characteristics, a one-dimensional model of the vibrator is derived. Using the method, a side-lobe level can be reduced to about 20 dB for the secondary wave in the parametric source.

Beam-Width-Controllable Ultrasonic Transducer Array

In this paper, we present a new method for beam width control of transducer array using two-layered piezoelectric transducers of which electroacoustic efficiency can be controlled by a capacitor. The measured result for beam width control of the transducer array shows good agreement with the simulation result. It is confirmed that the beam width of the transducer array is easily controlled by varying the second harmonic generation efficiency of each element.

In vivo Measurement Method for Nonlinearity Parameters Using Single Ultrasonic Transducer

A transducer consisting of two bonded Pb(Zr, Ti)O3 (PZT) disks is applied to measure the nonlinearity distribution in a layered biological tissue and an in vivo measurement method using the transducer is also investigated. The measured results of nonlinearity parameters of B/A are compared with the theoretical results calculated using equations in the literature, and good agreement between them is obtained. Consequently, the usefulness of the transducer in measuring the nonlinearity of biological media is successfully demonstrated.

A New Method of Calculating Radiation Impedance for Vibrating Surface with Finite Baffle

In this paper, by defining a vibrating surface to be a set of small point sources, a new calculation method for the rectangular vibrating surface with a finite baffle is suggested by considering the effect of the finite baffle on the source strength of each point source. As an example, the variation in self-radiation impedance for a rectangular vibrating surface is calculated based on the size of the baffle.

A new calculation method for the radiation impedance of square piston

In ultrasonic transducers, the calculation of radiation impedance is fundamental to predict the acoustic behavior of the transducers. Although the self and the mutual radiation impedance have been studied by many authors, the expressions of formulas for a rectangular piston are very complicated and hard to obtain analytic solutions. Accordingly, the solutions have been obtained by numerical integration with approximation. Because computational algorithms include multiple loops due to multiple integration, it takes a long calculation time and the results have low accuracy. In this paper, we propose a new algorithm in that the vibrating surface of the rectangular piston is divided into small elements and the duplicate calculations are recognized in the calculating process of mutual effects of each element. Using the algorithm, quadruple loops due to quadruple integration are simplified to single loop or double loops and the short calculation time and high accuracy can be obtained. As a demonstration, the self and the mutual radiation impedance for a vibrating piston with regular square surface are calculated and its calculation accuracy is evaluated.