The "clicks" are the notes that real stars make when they pulse. I saw a documentary about it, and the sounds are very similar to the ones reproduced in the gal map. In my opinion the gal map sounds are cosmetic: you can already tell the star type from the info tab. Regarding how many planets are inside the system, I don't think that star sound gives you hints. To me they all sound similar. In fact from a gameplay point of wiev it would be lame to have even more informations before actually exploring (entering and honking) a system. Also from a technical point of wiev my understanding is that a system is genrated when the first one jumps in, so if nobody has jumped into that system, even the starforge shouldn't know what's inside.
Of course as usual I might be wrong, but I hope they didn't put stuff that can give us more information before entering a system.
