Acoustic Equation and its program

General Discussion
1

Hello, I am somewhat new to FreeFEM. Using it for acoustic analysis. Can someone please help me in knowing how the example code is working. I’m unable to get:

  1. How the direction of flow is defined (it is given in documentation that sound is coming from left vertical border) in Acoustic example (under learning by examples)?
  2. What is ‘g’ there. It is given that it is source equation but from where do we get that and are there any other equations which could be used?
  3. What is ‘kc2’ defined in the program?
  4. Results are showing some values which are also in negative, so what are these values representing. Are these dB values or something else!
    Thanks in advance.
    Please, any fast help would be great!
2
  1. the flow is defined by the boundary conditions
  2. g is the Dirichlet boundary condition
  3. kc2 is equal to (k/c)^2
  4. the problem is solved in the frequency-domain
3

Thank you!
Could you please tell how it (g) is defined g=y*(1-y). Is it any standard equation or just as an example it is used and is there any other equation for this?

4

It is just a random BC. You can also use Neumann, Robin, PML…

5

Thanks a lot!
About 4. I just wanted to know that in results (graphical) shown after running program, we see isovalues. So in this acoustic example, is it correct that these are values of sound pressure level (in decibel)? I can’t find if there is any option to show the units of values in graphical results.

6

Someone please help me with this! (Previous reply).

7

There is no need to spam. u is the amplitude of time-harmonic solutions to
the wave equation at frequency k. You can have a look there.