If it sounds like its coming from inside the car its probably the fuel pump if not its kind of hard to say.
bad wheel bearings
Possibly worn wheel bearings can create a humming or groaning sound.
the bearings
A defective vacuum line can cause a whistling sound when the vehicle is accelerating. A loose belt can also create a high pitched whistle sound.
You may need differential fluid...check that.
Answer Humming noise from front endI just got my car fixed with the same problem and it was the wheel bearing and it is gone. Was it a fwd car?
When the wheel and the tire rub together.
The motor which blows air through the vents.
One would really have to hear it in order to determine for certain. Are there any particular conditions existing in which the humming occurs? Wheel bearings are a possibility.
if its a front wheel drive vehicle then it could be the axels
main shaft bearing
More than likely... the power steering belt.