1998 Ford Contour • 193,000 miles

Everytime I am about to get on the freeway or a street with a slightly high speed limit my car makes a whirring sound(almost like a turbine powering up). This only happens when accelerating towards a high speed, it happens on slow accelerations but very rarely. This has not caused any performance problems, but I would rather not risk any future problems. Could this be related to a crack in the exhaust manifold?
August 23, 2011.

If it's only happening at higher speeds, then you would have all the splash guards under the car checked. They can start vibrating in the wind and cause a noise like that.

Aug 23, 2011.
The sound is only made when accelerating to high speeds. Once the car reaches around 45mph+ during acceleration the sound stops or isn't as loud. Cruising at speeds around 20-45 mph will not make the sound. The thing is that since the performance of the car has not been affected at all, I don't know how serious this could be. I'm mainly worried that the car will make the sound when on the dyno at the smog check and not pass the inspection.

Aug 23, 2011.