You need to specify a tag when you play a sound to keep tracking it.
So you can use the expression Audio.volume("tag") to know what the current sound volume is.
Play "mysound", at 10db, tag: "mytag"
Audio.volume("mytag") will return 10
You can also use the condition: system/compare two values/audio.volume("mytag") greater than 0 -> do that
If you play all your sounds at 0db and the sounds themselves are either loud or quiet, then you can tag them "loud or quiet" when you play them to know which kind is playing.