Creating a Reference Plane Ultrasonic Wave in a Fluid Using a Plane Piezoelectric Transducer with a Large Wave Dimension
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SICAL PROBLEMS OF LINEAR ACOUSTICS AND WAVE THEORY
Creating a Reference Plane Ultrasonic Wave in a Fluid Using a Plane Piezoelectric Transducer with a Large Wave Dimension A. A. Krokhmala, *, D. A. Nikolaeva, S. A. Tsysara, and O. A. Sapozhnikova, ** aMoscow
State University, Physics Faculty, Moscow, 119991 Russia *e-mail: [email protected] **e-mail: [email protected]
Received November 1, 2019; revised April 27, 2020; accepted April 28, 2020
Abstract—The article discusses the possibility of using a plane piezoelectric transducer with a large wave dimension as the source of a reference plane ultrasonic wave, which can be used to calibrate hydrophones in the megahertz frequency range. In the experiment, the source was a piezoceramic disk with a diameter of 100 mm and a thickness resonance frequency of about 1 MHz. A method was developed for determining the sensitivity of the transducer in the transmit mode by measuring its electrical impedance. A methodology is proposed for finding the parameters of the plane wave component of the emitted acoustic pulse from a known electrical signal on a generator. It is shown that the acoustic pulse profile measured by a calibrated hydrophone near the source agrees well with the theoretically predicted signal. Keywords: piezoelectric transducer, hydrophone calibration, plane wave mode DOI: 10.1134/S1063771020050061
1. INTRODUCTION The problem of calibrating sources and receivers is conventional for acoustic research, in particular, in ultrasound applications in medicine, as well as in hydro- and aeroacoustics problems. An important characteristic of any electroacoustic transducer is its sensitivity, which is the relationship between its electrical and acoustic signals. For an acoustic receiver (hydrophone or microphone), sensitivity is understood as the ratio of the electric voltage arising on it to the acoustic pressure at the location of this receiver in its absence. Since any receiver has a finite size, its response to an acoustic field depends on the structure of the field at its location. This is why sensitivity is introduced with respect to a wave with a given structure; a plane incident wave is usually used. It is clear from the foregoing that the ability to create a plane wave with known parameters is fundamental in problems of calibrating receivers. Conventionally, the plane-wave mode is created by placing the receiver in the far field of the acoustic source. The disadvantage of this approach is the need for measurements at large distances from the source; i.e., the corresponding settings cannot be compact. In addition, in far field measurements, significant wave attenuation occurs. Lastly, the relationship between the electrical signal at the source and the corresponding acoustic signal at the receiver depends on many parameters, which reduces the calibration accuracy.
Currently, a large number of methods have been developed for calibrating acoustic sensors and finding acoustic field parameters: the reciprocity and self-reciprocity methods [1, 2], a method for
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