Sounds like an electrical 'spike' because you haven't got an anti-surge filter on your electrical supply. You should be able to buy a suitable power strip from your computer shop. Even better, a battery-backed power supply so your compyter keeps working long enough for you to shut down properly if there's a power failure, as they also have filters built in.

The pop pop pop, even with the volume turned down, seems to suggest a problem elsewhere... heating boiler, air-con, fridge, freezer or something. An anti-surge filter would stop those affecting your pooter.