The Xerces Society’s reply: “We haven’t heard of or read about noise or firework-associated concussion in bumble bees. Any comment would be total speculation.” Not that they can know everything, of course, but I’d take this as at least an indication that it is not a “known” issue.
Recent mass killings in Oregon were caused by application of neonicotinoid pesticide on trees to control aphids and their “sap” from dropping on cars.
And if you really want to get depressed, there’s this: http://www.end-times-prophecy.org/bee-die-off.html