A Parameter Study of Focused Sound Fields in Active Media
Focused sound fields ranging from very low frequencies (infrasound) in the sea to frequencies far into the MHz region, used for medical and industrial purposes, have received particular attention during recent years. Medical applications of focused ultrasound for diagnostic scanning of organs and for therapeutic disintegration of body stones, are of considerable interest to the Industrial Acoustics Laboratory at the Technical university of Denmark. A parameter study has been performed of the KZK-model in order to determine the applicability of this model for computational simulation of focused, nonlinear wave propagation in active media. Some modifications to the KZK-model introduced permit the computation of variations in frequency and time domain responses of axisymmetric nonlinear wave fields with linear focusing gains in the range of 200, e.g shock formation in the focal zone. Parameters considered in the evaluation include the relative influence of parameters describing nonlinear effects (B/A, fundamental frequency, source amplitude, etc.), diffraction effects (geometrical considerations), attenuation effects (absorption and scattering), and linear focusing gains with particular emphasis on wave distortion in and around the focal zone. The computer codes developed have been implemented to run on personal computers.
KeywordsPulse Repetition Rate Focus Ultrasound Finite Amplitude Source Pressure Focal Zone
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