When I play any sort of audio on my Mac, including youtube, iTunes, etc., I get an annoying constant popping in the speakers for the duration of the audio. I have determined that it is not the audio tracks themselves. I am running OSX Mavericks.
First guess would be an external electronic device causing interference. Unplug and move all external devices away from the Mac and see if it goes away. Then you can move them back one at a time.
Most likely it's a loose wire or faulty speakers. If these are external speakers, I'd recommend changing the cable if possible. If they are internal speakers, then you likely need service.
Given the range of software/services you are having this with, I'm hard-pressed to think it could be a software issue, however I just did a bit of googling and it's not unheard of. I'm going to post links to a couple discussions elsewhere with various tips and solutions.
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