How would one translate any Alien languge. We know how we equipped the Voyager probes. And we know the UAs are transmitting their locations in morse code (the human version). So any sounds that are left is the equvilent of Thargoid morse code or even speech. Dash dot dot dash dash...... equals Chirp Honk Chirp Chitter etc etc...... oh my my tinfoil is slipping. Thats the wonderful thing about humankinds first ever interaction with an Alien species. Except here we have very clear clues right in front of us "listen to them" and "look at them".
I would just like to point out that the above lore I have listed was written by non other than The Braben and his friends personally. The similarities to the current story and finds is almost frightening. Because if we stuff this up we could be starting an intergalactic war all over again. Even worse from what I have perceived from the past lore and the current lore is that Elite Dangerous is not even about Us or the Thargoids. There is something worse coming. And I speculate the Thargoids know it and are actually trying to enlist mankinds help to fight it. Why else would a race proven to be Superior to us in almost every way not wipe us out when they had the chance. Because they need help fighting an even greater menace that's out there.
The idea that the sound is a Rosetta stone for the alien 'language' is the simplest explanation for the sound yet. *And* it was mentioned very early on, too.
Except...
It would mean the sound designers haven't been quite as hot as they have been elsewhere, because the rest of the sound doesn't repeat at all from what anyone's been able to gather; and if the rest of it is the alien equivalent of the same system name, then it would have to repeat. I guess it's possible they didn't put as much effort into that part of the sound, but... Well, with the Morse we see evidence of dynamically generated sound based on location data; doing the same for alien sounds would be the same process, just with different sounds and logic, and I think they would have done so if that's what it is. I might have too much faith, though.