Look at the Bold and you'll see no hard code is involved.
Only the dsd file and the entry in the SH3.sdl file.
There is no entry in the SH3Sound.act file for it but it works!
Create the dsd for the snorkel just like the bold.dsd then edit the sdl to match.
You should get a sound only when you raise or lower it as it does not loop.
Of course the spawning of the Bold might trigger the sound where the snork is always there so sound may not work.
If that's the case some trickery might work.