I'm noticing a higher pitched whirring/ whining noise around the 40-mph range and above, whether accelerating or decelerating. Sometimes I think it's slightly louder when decelerating. Overall, it sounds as though the engine is working harder although the rpm dial looks to be in the normal range, no spiking or anything. There's nothing obvious in terms of lurching or slipping while driving, though I thought maybe I noticed something recently -- but if it was real it was very slight, and maybe my mind was playing tricks on me! The chronology: In March 2010 (about 27k miles), I had 4 new tires put on and the alignment done. I first noticed the noise at the end of May 2010. Mid June (at about 31k) I had the 30-thousand mile Service done...this mechanic as well as another one couldn't detect the noise I was referring to, which I could partially understand not knowing the typical sound the car made, (its 'baseline') like I do. With the sound persisting after the 30k Service, I wondered if there might be a new alignment issue and (at about 32k miles) I just had the alignment done again along with rotating the tires and having a visual brake inspection. No issues detected, but the noise still persists. In general, that smooth gliding feeling the car used to have on the highway isn't there anymore, again as though the engine is working harder. There's also a slight vibration I'm getting through the steering wheel. This higher pitched whining doesn't seem to correspond with when the green "eco" light comes on (indicating the engine is switching to gas-saving mode). My layman's guess was maybe transmission issues? Maybe the differential? Otherwise, I wondered a) if it's possible this is just a weird vibration the treads might be causing? (Doubt it, since there was no such noise the first couple months after the new tires were put on). Or b) if maybe there's an issue with the noise canceling mechanism I was told is built into my model Honda, to eliminate noise produced by the car using less cylinders when in gas saving mode (eco). This doesn't seem on target either, since once again I haven't noticed any correlation between eco mode and the presence of the noise. Any thoughts?