I've been having this problem very recently. Had my first HTC One since late October. Two days before New Years my top speaker "blew" for no apparent reason. Just a loud crackle sounds coming out of the phone speaker during calls or playing any type of sounds (Music, gps directions, etc.) Turning off Beats made the sounds worse (so likely hardware?). I sent my phone to Verizon for an exchange for a referb. Got the replacement phone this Monday, and this evening (2 days later) I'm presented with the exact same problem!
I'm rather clueless what would be causing this. I work in a rather dust-less environment and speakers are mostly used for GPS / speakerphone on occasion. I've never had to replace a phone due to a defect for the past 10 years. Having 2 defects in under a month is quite frustrating and doesn't give me much confidence in HTC if this has been a known problem.
I really want to love this phone, but the past posts on this thread is giving me more reason to jump ship to the Galaxy S4 while I still can. Would that be over-reacting and should I give HTC referb another chance? (3 times the charm?)