Mac noise
I have to say I've never heard that sort of noise coming from any kind of computer, but it definitely doesn't sound good 🙁 So, you may want to seriously consider taking it to an Apple Store (if possible?) where they should at least be able to diagnose it free of charge. Then after that they will first let you if it is even fixable, and if so, they should also provide you with an exact estimate of how much it would actually cost for them to repair the problem. However, I did google 'mac laptop making buzzing noise' and found that you're certainly not alone, so you might wanna start there 😉 Good Luck!