acceleration noise

[mojo719]

When under light acceleration and the speed is just below 30 mph and until I hit about 40mph (1750 to 2250 rpm range), there is a very deep/low pitch noise coming from the engine. When its doing this you can also feel a vibration similar to what you feel when the bass on a stereo is set high. The car is an automatic but it feels like you are driving a manual and trying to accelerate at 30 mph but you are in 6th gear. I can't tell if it is coming from the intake? Fuel injection/fuel system not putting out enough? Or worst case something in the transmission? The vibration feels more like its coming from the engine compartment but you can feel it down the center console.

Any ideas? Thanks!!!