Just like the subject said, it is the tower sounds. They are messed up. Anything that has to do with the tower and sound is always glitching in and out. Mainly happens with anything that has to do with the items and the people like vangard, crucible, etc when you hold square to approach.
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Yeah, for me, sometimes the ambient sounds cut out, but it happens the most when I'm trying to interact with an npc. Their dialog clips cut out; forcing me to read the subtitles.