[CIG-SEISMO] source term definition in acoustic simulation

[Yingzi Ying]

Hi Guys,

My initial purpose is to use a loudspeaker to play an audio wavelet, 
which is recorded by a microphone(sound pressure signal), to reproduce 
sound field, that I need a system with sound pressure signal in and 
sound pressure signal out.

I take a look at the source term definition in the Daniel's 2011 paper 
"Forward and adjoint simulations of seismic wave propagation on fully 
unstructured hexahedral meshes". It says "The source f may be expressed 
in terms of pressure P" as in Eq(12), but intentionally denotes with the 
capital letter "P".

I do a simple test with Specfem2d, in which I put a co-located source 
and receive. I see that the scaled horizontal or vertical displacement 
waveforms are exactly the same as the input signal waveform. Then I 
guess the source signal term is more related to represent the 
omni-directional volume injection rather than pressure.

As the homogeneous PDEs governing the pressure and displacement 
potential have the same form, to meet my initial purpose, I input a 
signal and record negative displacement potential as output. The output 
signal(reproduced sound) is very similar to the input sound wavelet. The 
difference may due to the 2D simulation(2D Green's function response).

Could you please let me know if such tricky way may have any problem? Or 
do you have any suggestion to a more safe/better way to define the 
source signal as sound pressure?

Many thanks and regards,
Yingzi