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Bioacoustic range equation

Opieliński K. J., Gudra T.

Hydroacoustics

2016

Vol. 19

307--318

In order to describe and analyze the bioacoustic link, the authors of this study used a modified range explicit equation formulated for a hydroacoustic link. The equation makes it possible to design a bioacoustic link by assuming a given study range in a biological medium, and estimating the required power ratio or power level drop, and then selecting a value for the ratio by means of ultrasonic transducer parameters. A biological medium submerged in water between a transmitting and receiving ultrasonic transducer was studied in a streamlined manner as quasi-homogeneous, or more specifically, in the form of a multilayered tissue structure with parallel border surfaces. In the paper, sample calculations of the relation between power level drop and the length of the bioacoustic link in biological media, for ultrasonic wave frequency in the range of 1 – 5 MHz were performed; using a modified range explicit equation formulated for a hydroacoustic link. The calculations were verified in an experiment.

Determination of the B/A of biological media by measuring and modeling nonlinear distortion of pulsed acousticwave in two-layermedia

Kujawska T.

Hydroacoustics

2008

Vol. 11

149-158

The acoustic nonlinearity parameter, B/A, is a fundamental material constant characterizing nonlinear properties of biological media. Knowledge of the B/A of biological fluids or soft tissues through which pulsed acoustic waves generated from clinically relevant probes are propagating is necessary whenever high intensity pressure fields are produced. The numerical model recently developed in our lab, capable of predicting the pulsed sound fields generated from axisymmetric sources in nonlinear attenuating media, was a powerful instrument for investigating nonlinear acoustic fields produced from circular plane or focused sources in attenuating media in dependence on boundary condition parameters. Quantitative analysis of the obtained results enabled developing the alternative method for determination of the B/A parameter of biological media. First, the method involves measuring in the near field of a piezoelectric transducer the nonlinear waveform distortion of the pulsed acoustic wave propagating through the two-layer system of media: water-tested material. Then, the method involves numerical modeling, in frequency domain and under experimental boundary conditions, the nonlinear waveform distortion of the propagating wave by using the Time-Averaged Wave Envelope (TAWE) approach [1]. The obtained numerical simulation results were fitted to the experimental data by adjusting the B/A parameter of the tested material. The determined values of the B/A for standard media considered (corn oil, glycerol, pig blood, homogenized pig liver), whose density, sound velocity and attenuation law have been preliminary determined experimentally, are in a good agreement with those published. The proposed method ensure the decimal degree of accuracy, is relatively simple to use and requires small volume of tested materials that is important because of difficulty of their availability.