k-Wave

1. tcr11
   

   Member
   Joined: Feb '16
   Posts: 2

   Hi

   I've setup a simple 3D k-wave simulation with a single cell point source and a full plane of receivers for an US tomography problem. Before adding extra complexity to the sim I would like to treat the medium as homogeneous with the density of water (c = 1500 ms-1), without dispersion (medium.alpha_mode = 'no_dispersion') and be able to detect the time of flight (TOF) from the source position to each point in the receive plane. However, when attempting to flatten this response for water using an ideal TOF found from the known distances and speed of sound I find that they do not match the detected TOF. How would I minimise the affect of absorption and simplify the simulation to prevent this?

   TOF mismatch: https://i.imgur.com/UEHTUI4.png

   All the best
   Tom

   Posted 6 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Tom,

   Do you get the correct speed with no absorption (i.e., leave the absorption parameters undefined)?

   Brad.

   Posted 6 years ago #

3. tcr11
   

   Member
   Joined: Feb '16
   Posts: 2

   Hi Brad

   Shortly after posting the question I found that the problem was largely caused by a sampling error which selected the wrong point in a plane of receivers: once corrected for (and with absorption parameters undefined) it started to produce something that was more correct.

   In a related question, if an input signal was given to the kWaveTransducer source struct as a wavelet, does k-wave prepend the signal with zero values? I've noticed the TOF is still a little larger than the ideal case.

   Example: https://i.imgur.com/dpmwHVp.png
   Wavelet: https://i.imgur.com/NWyg5ks.png

   Cheers
   Tom

   Posted 6 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Yes, it pads the signal. There are more details about how to control (and query) this in Section 3.7 of the k-Wave Manual.

   Brad.

   Posted 6 years ago #

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