I'm on a Mac Pro using Sierra 10.12.6. Over the last few months, this problem has become more and more frequent. When playing an audio file (or video with audio), if Firefox is open, my entire system's sound will start "stuttering," for lack of a better word. It does it so quickly that the audio sounds like a buzz. If I quit Firefox, everything returns to normal. I can even re-launch Firefox and play the same video or audio file, and it will work perfectly for a few hours, then it will happen again, and the only solution I can find is to quit Firefox and relaunch it (which is inconvenient if I happen to be also downloading or uploading at the time). BTW, the video continues to play normally--it's the audio that is screwed up--for any application that uses sound (iTunes, VLC, other browsers, etc).

Anyone heard of this happening before? Any suggestions of how to eliminate the problem?