Well first your going to have to buy about 3000sq feet of copper screen :crackup: and then cover all the walls and floor and ceiling of that room your in and then your
going to need 10ea 8 foot long copper coated steel ground rods driven in at least 7'6" into the ground all around that room and connected with some
No.#8 gauge wire to 10 spots evenly placed around the room, don't forget to make a door way so you can get in :crackup:
And that should take care of the problem
Seriously get some tin foil and cover the inverter and ground it to the negative side of the supply and cover anything else you can that has to do with 90 volts 400hz.
of course you can not cover the EL wire it's self with tin foil but get every thing else you can.
If you do it in steps like the inverter first maybe that will be as for as you have to go.
just keeping the two circuits apart as far as you can could help.
Also shielding the components of the LPM can help also but it's shielding must stay separate from the shielding of the 400 Hz.
for the EL wire if you have to go this far, you can tape it on the inside wall with some 1/2 wide copper tape like what is used for stain glass window work.
Tape it to the inside wall and solder a wire to the tape at one end first and ground the wire to the negative side of the supply.
In addendum it is normal to connect the shielding to the negative side of the supply, but sometimes it works if the shielding is floating or not connected to anything.
I'll send you some zirconium foil if you want
Hope this gives you some ideas :beer: