How to achieve a transition effect from the outside of a wall to the inside

I need heard a band from outside a room and then from inside. Listen to the band as if you were about to enter a pub and then enter to the pub to hear the music clearly. With snapshots? With Eq? Thanks and sorry my english. I make the inverse procees with EQ and Snapshots, but is not allright because when I enter the room it sounds as if I was about to enter.

You can use a few different methods. The most common one would be to use snapshots to detect if you are inside or outside the pub. When outside the pub, you can apply a lowpass filter and some room reverb (pre-spatializer). When inside, these effects no longer apply.

You can also look into occlusion. Some integrations like the Unreal Engine integration have a built in occlusion support, or you can add it yourself manually.