Term is Vacuum cleaner not Hoover that's as we all know is a make of cleaner.
My guess, but you've probably found that out already, if the motor noise changed pitch to higher tone then the tube is blocked. Another is the obvious hand over the tool end see if their is any suction. Try pop the ring tabs in on the tool and machines ends (some just screw in as the tube is like a thread.) then push a bamboo cane down the tube to clear.
Bob, August 2015