Whenever you join a friends party while in-game, you can only hear them if you have the party "snapped" if you unsnap it, you wont be able to talk to your friends unless you exit the game completly. Something Bungie should know about and fix.
English
#feedback
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I had the same bug. Had to do a hard reset of my system. I found there was a high pitch buzzing noise as soon as I opened party chat in addition to the problem you have outlined here.