k-Wave

1. lirj
   

   Member
   Joined: Jan '15
   Posts: 9

   Hi Dr. Treeby and Dr. Cox,

   I have two questions about the ultrasound simulation in the hemerogeneous medium.

   (1) I used the function "toneBurst.m" to generate the excitation pulse signal. And the ultrasound propagations is simulated in a heterogeneous medium.
   Is f_max the double central frequency of the excitation pulse signal [ The equlity is PPW = c_min/(f_max * dx) ] ?

   (2) When I simulated with the kspaceFirstOrder1D.m, the command window would print the value of the maximum supported frequency. Is f_max and the maximum supported frequency the same parameter?

   (3) The excitation pulse signal emited by sensor A, is propagated through a heterogeneous medium, and the transmission signal is received by sensor B. How to avoid the deform of the transmission signal ? To make it as the case that through the homogenous medium, only has the time delay and the amplitude reduction.

   Could you help me to solve these questions? Thanks.
   Best Regards.
   Lirj

   Posted 7 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Lirj,

   (1) The maximum frequency present in a toneburst will depend on the number of cycles. The longer the toneburst, the more narrow the frequency spectrum. You can use the function spect to look at the frequency spectrum of the pulse you've created.

   (2) The maximum frequency printed to the command line is calculated from the grid spacing and sound speed, and represents the maximum frequency that can be represented on the spatial grid. It doesn't report the maximum frequency actually contained within your source. If you want to restrict your source to the maximum frequency supported on the grid, you can use the function filterTimeSeries.

   (3) I'm not sure what you mean by deformation of the transmission signal. Do you mean due to numerical dispersion? If so, you can reduce this by reducing the size of the time step.

   Brad.

   Posted 7 years ago #

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