Computing and measuring nonlinear and linear propagation by two independent methods

• Autorzy: Filipczyński L. , Kujawska T. , Secomski W. , Tymkiewicz R. , Wójcik J.
• Języki publikacji: EN

Abstrakty

EN

Nonlinear effects, caused by propagation of ultrasonic pulses with finite amplitudes, were computed and measured in water in the case of pulses with pressures up to 1.5MPapp used in diagnostic devices. An electronic transmitter generated high (280Vpp) and low (47Vpp) voltages, applied to a plane PZT transducer causing in this way nonlinear and linear propagation effects. The carrier frequency of the pulse was 2MHz, while its time duration was 2.5\,ms. The measurements were carried out by means of a typical calibrated PVDF membrane hydrophone and by an electromagnetic (EM) hydrophone, prepared for this study. The pulse measurements by means of the PVDF hydrophone showed a higher number of spectral components than those by means of the EM hydrophone. This effect was explained by sensitivity characteristics that increased in the PVDF and decreased in the EM hydrophone as a function of frequency. Previously, it was shown that the effective frequency band used in measurements by means of the PVDF hydrophone is situated below the resonance, on the increasing slope of the resonanse curve. The properties of the EM hydrophone were analysed on the basis of the plane wave assumption. A procedure was developed to correct distortions of the pulse spectrum and its pressure measured by PVDF and EM hydrophones. In the first case the maximum peak-to-peak pulse pressure should be decreased by 27%, while in the second case it should be increased by only 0.7%, and by 3% if an additional amplifier was used. The sensitivities of PVDF and EM hydrohones were very different and equal for the frequency of 2MHz to 28mV/MPa and 0.10mV/MPa, respectively. The calibration of the EM hydrophone was carried out by means of only two simple: electrical and magnetic independent measurements, although in the EM hydrophone there occured external interferring signals. For the theoretic-numerical detemination of the acoustic fields and their spectra generated in the case of nonlinear and linear propagation the numerical procedure called the WJ Code was applied. It was developed recently by the last-named author of this paper. In calculations absorption in water was taken into account. The critical distance, where distortions caused by nonlinear propagation in water were maximum, was determined by a number of computations of the ultrasonic field as a function of the distance from the transducer. A good agreement between computed results and those measured by two different methods, showing the pulse pressure distribution along the whole beam axis, was confirmed. In this case it was shown that the ?/4 matching layer covering the transducer surface influenced the edge wave radiated by the transducer.

Słowa kluczowe

EN

ultrasound; nonlinear propagation; pulses; diagnostics; hydrophone

• Wydawca: Instytut Podstawowych Problemów Techniki PAN ; Komitet Akustyki PAN ; Polskie Towarzystwo Akustyczne
• Czasopismo: Archives of Acoustics
• Rocznik: 1999
• Tom: Vol. 24, no. 3
• Strony: 269--288
• Opis fizyczny: Bibliogr. 19 poz., rys., tab., wykr.

Twórcy

autor

Filipczyński L.

autor

Kujawska T.

autor

Secomski W.

autor

Tymkiewicz R.

autor

Wójcik J.

• Polish Academy of Sciences Institute of Fundamental Technological Research, Department of Ultrasound, 00-049 Warszawa, Świętokrzyska 21, Poland

Bibliografia

• [1] M. Averkiou and M. Hamilto n, Nonlinear distortion of short pulses radiated by plane and foused circular pistons, J . Acoust. Soc. Am., 102, 2539-2548 (1997).
• [2] A. Briggs, Acoustic microsopy, Clarendon Press, Oxford, UK 1992, 35.
• [3] F. Duck and K. M art in, Exposure values for medical devices in ultrasonic exposimetry, M. Ziskin , P. Levin [Eds.], C R C Press, Boca Radon, Florida 1993, 329, 333.
• [4] J . Etienne, L. F il ip czyńsk i, A. Firek et al., Intensity determination of ultrasonic focused beams used in ultrasonography in the case of gravid uterus, Ultrasound in Med. and Biol., 2, 119-122 (1976).
• [5] J . Etienne, L . Filipczyński, A. Grabowska and T . Waszczuk, Pressure measurements by means of foil and capacitance hydrophones in nonlinear acoustics, Proc, of the X X X V Open Acoustic Seminar, Białowieża - Warszawa, Institute of Fundamental Technological Research, Vol. I, 266-271 (1988).
• [6] J . Etienne, L. Filipczyński, T . Kujawska and B. Zienkiewicz, Electromagnetic hydrophone for determination of pressures of shock wave pulses, Ultrasound in Med. and Biol., 23, 747-754 (1997).
• [7] B. Fay, P .A . Lewin , G . Ludwig, G .M . Sessler and G . Yang, The influence of spatial polarization distribution on spot poled P C D F membrane hydrophones performance, Ultrasound in Med. and Bio l., 18, 625-635 (1992).
• [8] L. Filipczyński, Absolute measurements of particle velocity, displacement or intensity of ultrasonic pulses in liquids and solids, Acustica, 21, 173-180 (1969).
• [9] L. Filipczyńsk i, J . Etienne , G . Lypacewicz and T . Waszczuk , M era surement technique of shock wave pulses at extremely high pressures, Archives of Acoustics, 21, 37-51 (1996).
• [10] L. Filipczyński, J . Etienne, T . Kujawska, R. Tymkiewicz and J . Wójcik , A multilayer method for linearity determination of the P F D V hydrophone pressures up to 2.3 MP a, Archives of Acous¬tics, 23, 513-520 (1998).
• [11] L. Filipczyński and A. Grabowska, Deviation of the acoustic pressure to particle velocity ratio from the pc value in liquids and solids at high pressures, Archives of Acoustics, 14, 173-179 (1989).
• [12] L. Filipczyński, T . Kujawska, R. Tymkiewicz and J . Wójcik , Nonlinear and linear propagation of diagnostic ultrasound pulses, Ultrasound in Medicine and Biology, 25, 285-299 (1999).
• [13] L. Filipczyński, T . Kujawska, R. Tymkiewicz and J . Wójcik , Computing and measuring of nonlinear propagation effects by means of P V D F and EM hydrophones, Paper presented at the 15 International Symposium on Nonlinear Acoustics (15IS NA), Goettingen, Germany, 1-4 September 1999.
• [14] G . Lypacewicz and L. Filipczyński, Measurement method and experimental study of ceramic transducer vibra tions, Acu stica, 25, 1, 64-68 (1972).
• [15] G . Lypacewicz, A. Nowicki, R. Tymkiewicz, P. Karłowicz and W. Secomsk i, Acoustic field measurements using a P V D F foil hydrophone, Archives of Acoustics, 21, 361-369 (1996).
• [16] W .P . Mason, Electromechanical transducers and wave filters, Van Nostrand, 1948.
• [17] J . Somer, J . Corsel and H. Van der Voort, Evaluation of a computer-model for P V D F trans¬ducers of arbitrary configuration, Archives of Acoustics, 13, 127-135 (1988).
• [18] J . Wójcik, Conservation of energy and absorption in acoustic fields, J. Acoust . Soc. Am., 104, 2654-2663 (1998).
• [19] J . Wójcik, see the section Basis of numerical procedures in the reference 12.