Very loud (buzzing) grinding noise during

For the past several months my car has been making a horribly loud buzzing/grinding noise underneath the hood area.

Background information: I get the oil changed every 3,000 miles and just had the serpentine belt changed last week before leaving for vacation. The belt was fraying. I was told my water pump may be leaking, to pay attention to spots left underneath the car and that in the future I would want to go ahead and replace the water pump. Also, my engine light just came on and hasn't gone off. (Been on since last Monday) Usually, it was because of me not having tightened the gas cap (emissions) and once done correctly and after several trips the light would go off. One of the prior times the light came on I had a friend hook my car up to a diagnostics machine. He said the light had something to do with the emissions and there would be a part I would need to purchase for the car but not to worry about it because this type of thing wouldn't harm the car (I would notice black smoke/odor coming out of car but that was it). Also, at times I would change gears in the car as if it was a manual. (2nd gear to drive-which I've heard is bad)

Noise: I first noticed the strange noise coming from underneath the hood area when I was making a right-hand turn. Of course my car had slowed down and when I was making the turn and speeding up (probably around 2nd gear) I could hear a loud buzzing noise ehh! Almost sounded like a dryer buzzer going off. I then noticed the noise while going up an entry ramp for a mountain road and I was turning right. From there I heard it while going on a straight road - beginning acceleration. And I've heard it while slowing down again to go around a curve but this time going left.

The noise is so loud that people outside the car can hear it and actually turn around and look to try and figure out what the noise was. It doesn't do it all the time but is beginning to pick up its pace.

Any information is appreciated.

Thank you,
Tanya in Virginia