Why does your 2004 impala have a humming noise when you drive?

If it is coming from the rear of the car it is probably the fuel pump. Can be the fuel filter is partially clogged and it is working hard to pump the fuel. replace the fuel filter. Can be tire noise caused by a defect in the tire. Can be a defective wheel bearing. You need to isolate the hum. Or it could just be that your '04 Impala is happy.