k-Wave

1. ffarias
   

   Member
   Joined: May '14
   Posts: 9

   Hi there,
   I´m simulating the parametric acoustic array, and the results have been good so far, the ultrasonic waves are capable of produce a demodulated sound wave.
   By now I´m trying to compare these results with real measurements of the acoustic field. For that I´ve been trying to use a signal generated by a parametric loudspeaker as the source in the simulations, but it seems considerably different to what I´ve measured.
   I wonder if there is a problem with using an external source? It looks like the wave after some distance from the source has been filtered, the high and low frequencies are highly attenuated, so the spectrum looks very different.

   Kind regards,

   Felipe.

   Posted 9 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Felipe,

   The first thing to check is whether the frequency content in your external source signal is supported by the simulation grid. I normally suggest that you use filterTimeSeries to eliminate any unsupported frequencies before running the simulation. If the signal is altered in the same way after calling this function (but before running the simulation), then this is likely the culprit.

   Another thing to check - is the time step in your simulation set to match the time step of your experimental data?

   Brad.

   Posted 9 years ago #

3. ffarias
   

   Member
   Joined: May '14
   Posts: 9

   Hi Bradley,
   Thanks for your answer. I checked both but I still get the same results, changing the time step fixed the low frequencies problem though.
   After about 50 kHz the signal seems to be attenuated (I expect attenuation at high frequencies, but not like that). I increased the maximum frequency, the points per wavelength, CFL, even the values of attenuation but still no changes.
   Can this be a problem for using an external wav file?

   Posted 9 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Felipe,

   There shouldn't be any problem with using a external wave file (or indeed any source), provided the simulation parameters are set correctly. If you create a source containing the same frequency range as the wave file (e.g, a windowed sum of sin waves), do you still get the same results? If you provide a link to your code and source, I can try to take a look.

   Brad.

   Posted 9 years ago #

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