I've noticed an issues that a few others have confirmed. Sometimes, when decrypting engrams, picking up post master items, taking things from the vault..or even the odd gun shot sounds don't happen. I posted this out on a Destiny Community page on Facebook and a few other people have said they have found the same issue. Please note: it doesn't happen all the time, just every now and again. Sometimes it lasts a while and other times it goes away quite quickly.