Cut the high frequencies and bump up the bass a touch. Maybe add just a tiny bit of reverb, depending on the size of the room on screen.
Welcome to the forum.
Do you have Audition? There are some EQ Presets that will probably get you pretty close to what you want, and then with a bit or Reverb (the wall acting like a sounding board), the effect should be complete. Do not know if Soundbooth has those same Presets, but can probably tweak things in its EQ manually. I'd start by attenuating everything above about 500 Hz, incrementally for each frequency band, to simulate the higher ranges being absorbed by the wall. Perhaps a bit of a boost in the 125 Hz range. Trial and error, with critical listening should tell you how you're doing. I'd not brighten the human speech frequencies too much, and work on attenuation of other bands more. The Presets that I mentioned would give you some starting points, and possibly save you a bit of initial work - they just might speed the process up a bit.
[Oops: look like Jim beat me to it... ]
Thanks for quick answear, it worked like a charm