Low fluid level.
Certain types of tires may cause a brief humming noise after your initial acceleration. The transmission may also cause a brief humming noise.
The fuel pump is engaged.
Wheel bearing.
Could be a bearing going bad.
Check the bearings.
Check the wheel bearing.
the humming noise is coming from a bad ground on you stereo
wheelbearing or cv axle enjoy
radiator fans running to cool engine...
Irregular choppy wear in a tire, bad wheel bearing.
Where is the noise coming from? If its from the fenders or wheels is a much different problem than if its coming from the transaxle.
Power steering pump worn, or low on fluid