Yeah, this one's common. That noise means something is interfering with the blades, likely a foreign object left in the container or the container isn't seated right.
Turn it off and unplug it immediately. Check the container. Did you leave a spoon, fork, or the lid plug inside? Foreign objects will damage the blades and cause that noise.
If the container is clear, check the seating. The container's drive spline must be fully engaged with the drive socket on the base. Make sure the container is flush with the centering pad.
If that didn't work, inspect the blade assembly. Never operate with damaged blades. If you see chips or bends, stop. You need to contact Vitamix Customer Service.
Heads up: Always check the container is empty and correctly seated before you start. And never, ever operate with the centering pad removed.