1998 Mercury Marquis Whining noise

1998 Mercury Marquis 82000 miles

2 days ago the car was making a whining noise while driving. It would increase and decrease according to the pressure on the accelerator. The noise persisted even when the car was not moving. As we are an elderly couple we puit the car in the garage to decide what to do. Today, I checked all the fluids, filled any that were not full, started the motor and the whine is still there. It increased with stepping on the accelerator and when I let up, the whine was still there tho not as loud. I would appreciate a word of probable cause so that I will be able to check on a repair cost.