2007 Chevrolet Malibu Engine Resonance at Certain rpm?

[Xiaozhou Zhang]

I just bought a 2007 Chevrolet Malibu. I found that when the speed of the engine reaches 1250 or 2750 rpm, there will be a noise come from the engine. It heard like resonance and it will be much louder at 2750 rpm. I also can feel it a little bit from the steering wheel.
This kind of noise only comes when the engine speed reaches the indicated certain rpm.
Can any one tell me what is the problem?
Thank you very much!