Coupling Electrostatic, Structural and Acoustics

I am currently trying to couple 3 different physics for my electrostatic transducer. The coupling works in the following mode: Bias or static mode and time harmonic / frequency response mode.

For bias mode:
Electrostatic is used to bias the membrane at 300V, this have been performed independently with Electrostatic and Stuctural coupling, using the moving mesh, with boundary edge load set at stuctural to be Fes_nTr_emes, Fes_nTz_emes.

For frequency response/time harmonics:
However, I am stuck on the second mode, the time harmoning for a fully couple system which uses the small signal analysis (SSA) I am using the beam example for the SSA.

The main problem that is the last copling between the acoustics and the stuctural.

For Stuctural -> Acoustics (I am using the stuctural accelelation) : nR_smaxi*uaxi_tt_smaxi+nZ_smaxi*w_tt_smaxi

For Acoustic -> Stuctural (I am using the pressure and inserted in to the boundry (edge load) : nr_acpr*p2

However, since the same edge load is also used for the small signal analysis load (Fes_nTr_emes, Fes_nTz_emes), I am a bit puzzle here. Should I add the pressure to the Fes, or minus the pressure from Fes or is there any other way that I could do the final coupling for the fluid load.

I have tried to add and remove the load from Fes by doing the following such as:
Fes_nTr_emes +/- nr_acpr*p2

but it does not give me the frequency response that I am expecting.


I hope somebody could help me in this.