you did not mention where the buzzing sound was coming from. this is IMPORTANT.
-if the buzzing is coming from your psu this could mean it is unstable. if this is the case i'd replace it as a bad psu can wreck everything.
-if the buzzing is coming from a case fan or heatsink fan or video card fan this could mean that the lagging is caused by high temperatures. safeguards are often in place but still you should get this fixed
-if the buzzing is coming from the motherboard speaker/case speaker this normally indicates that either the speaker is bad or getting interference (doubt it) or there is an issue.
-if the buzzing is coming from something else this might mean other things.
also you did not mention if the computer had these problems since the START or if they occured AFTER installing something. for instance if your pc worked fine for 3 months and then you upgraded drivers and started having trouble. bingo bad drivers is most likely the cause.
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when we ask you to check for things, it is wise check for everything we say (theres a reason) and report back all the information you can. the more information (within reason) that you give back to us, the better information we can give you.
at this point in time i cannot say whether it is hardware or software. depending on the two questions you didnt answer it could give you a lead to where the problem may be.
another important question is the nature of the event. does the pc totally hang up for a few seconds (mouse doesnt move, screen has no motion, etcetera) or does it just slow down for a few seconds (mouse moves slowly or glitchy, framerate slows but doesnt stop, etcetera). does audio slow down, glitch, or stop entirely for that time period? what does the performance monitor (ctrl+alt+del, task manager, performance tab) say when the event happens? if it spikes go into the advanced area and look to see what program seems to be spiking.