...seconds or so.?
its not the brakes.. its coming from under the engine.. i jacked up the car and put up the cruise control and heard this oud vibrating sound from under the car... i popped the hood and puy a pvc pipe onto the hole between the engine and the radiator and i heard it even louder... its NOT the seat belts tho...

if it's not the brakes, it might be a bad belt or bad a/c compressor.

The first thing I would check are the belts. It may be as simple as tightening the tension adjuster.

After that I would check the bearings in the pullies and the AC clutch. If the bearings are going bad in the AC,Power Stearing, or Alternator you just replace the whole thing.

There must be some problem in the compressor.Need to change it.