Based on some comments on Reddit https://www.reddit.com/user/AnnoDelSignore13144/
I did this,
Add an AudioVolume.
Added 2 Ambient Sound Actors and assigned my SoundWaves.
One has no spatialisation the other Ambient Sound inside the volume has Attenuation(Spatialisation) inner radius slightly bigger than the AudioVolume.
Both Ambient Sounds have a SoundClass with the SoundClass property Apply Audio Volumes enabled
Both SoundWaves are set so they Loop AND under Voice Management set ‘Virtualization Mode’
to Play when silent. (else when you cant hear them, they stop playing and never play again, plus they keep playing rather than restarting)
The Audio Volume is set like this
the overall efffect is when you are outside the AudioVolume the main music is playing out, audible everywhere at full volume. As you approach the volume it sounds like outside a nightclub with muffled sound. Inside the AudioVolume, the sound quickly changes to become clear and you cant here the outside .
Unreal 5.3
AnnoDelSignore13144 said “The whole system of “audio volumes actors” attenuation only works on sound actors put in the scene as “ambient sound actors” regardless of having assigned a class with “use ambient volumes” ticked. All the other sound actors / cue apparently cannot in any way be influenced by audio volume actors.”