I don't think it's a hardware problem. After a few days/weeks of uptime, coreaudiod sometimes gets into a state where, regardless of output volume, it glitches and pops periodically until you force-quit it. It's like the daemon's internal state degrades such that it's just on the edge of able to feed audio buffers to the hardware fast enough, and then all bets are off as to whether other system load will tip it over into glitching.
Things seem worse if you have and switch between multiple audio devices. I filed a Radar on this (or a very similar bug) many OS releases ago that's still open with no feedback. But "restart your computer" also solves the problem, whether or not you follow the other placebo troubleshooting nonsense.
Things seem worse if you have and switch between multiple audio devices. I filed a Radar on this (or a very similar bug) many OS releases ago that's still open with no feedback. But "restart your computer" also solves the problem, whether or not you follow the other placebo troubleshooting nonsense.