I don't know quite yet if it's actually an issue yet, but it seems odd that the normal guardian's sound effects are very loud compared the the elder guardians, which you have to be very close by to hear them. It does not appear to effect the bubble laser sound.
MC-94110
Guardian Sound Volume Issue
Resolved
Duplicate
0
Nathan Griffiths
(Unassigned)
Unconfirmed
Minecraft 15w49a, Minecraft 15w49b, Minecraft 15w50a
Retrieved
I'm pretty sure that this was intentional, but if you don't like it you can change it with a resource pack (if you can find one)