HW7 ME720 Acoustics 2

Problems from Blackstock:

Use the Angular Spectrum code presented in class to do the following problems.

For the default source condition (f=2e6; a=1.5e-3; c0=1500;) compare the axial result with that of the exact result described in Chap. 13 of Blackstock. At what range do the solutions no longer agree? How is the result affected if lenx or xmax are changed?
Convert the initial condition m file (circsource.m) to that of a circular focused source with a radius of curvature specified by by the variable roc Email me your m file with a filename the same as your name, for example, my file should be cleveland.m
For the case f=2e6;a=10e-3;c0=1500;roc=60e-3; find the appropriate grid parameters so that the angular spectrum in the focal plane agrees with the result obtained in class for Fresnel diffraction. Start with lenx=256; xmax=5*a;
Plot the axial pressure field from 10 to 100 mm. What is the peak pressure and at what location does it occur? How many nulls exist along the axis?
What is the length and width of the focal spot based on the -6dB contours?

http://people.bu.edu/robinc/me720/hw7.html

April 2009