Time domain acoustic simulation- problem with the number of periods

[Annalisa]

Hi,
I'm trying to simulate a sinusoidal burst of 30 ms
(f = 250 kHz).
So, I set the number of periods at 7500 and the number of samples = 8000.
The problem is that when the simulation finishes, the solver recorded only 250 microseconds.
Other tests:

• periods= 1000, samples = 1001. Ok (recorded a stimulation duration of 4 ms)
• periods = 3000, samples = 3001. recorded a stim. duration of 2 ms !!! Something wrong again...
  Is there a limit in the number of periods one can choose?

Thanks a lot for your help

Annalisa

[montanaro]

Dear Annalisa, what do you mean by number of samples? Where do you see that?

We used to have a problem where we used the number of time points simulated was limited due to the type of integer used to store the number of iterations (unsigned short has a maximum value of ~65000, so by setting a number larger than that it would 'wrap around', so 70000 iterations would turn to 5000), but I thought I fixed it (it's possible I never pushed the changes).

In the simulation log file, can you check the total number of iterations for different number of periods? (say, 100, and then 1000 and 3000)

If the error is what I mentioned above it's something easy for the developers to fix but would require a new installation

[Annalisa]

@montanaro Dear Montanaro,
thank you for your fast reply.
By number of samples I mean the max number of time points recorded that I can set in the sensor properties.
I did several tests as you suggested and the error would seem that you mentioned.

• 90 periods --> 4759 iterations
• 100 periods --> 5288 iterations
• 1000 periods --> 52871 iterations
• 1229 periods --> 64978 iterations
• 1323 periods --> 4412 (it would be 70000)
• 3000 periods --> 27539 iterations
• 7500 periods --> 3311 iterations

How I can solve this problem?
Thank you

Annalisa

[montanaro]

seems I never pushed the code fix then.. I don't think there's anything you can do about it unfortunately from your end. I'll bring it up with the development team to see if they can provide you with an updated acoustic solver and fix it for next release

[Annalisa]

@montanaro That would be of great help.

Thank you so much
Annalisa