[skittlzski]

I have a Frigidaire basic dishwasher. The wash cycle sounds like it is not "agitating." There is only one sprayer at the bottom with the telescope. When I open the door during the wash cycle, the telescope seems like it does not come up and the sprayer sounds like it is not spinning (it sounds like it spins at first). The dishwasher sounds like it it an airplane taking off.

 

[Chemist1961]

The components I've seen in my old dish washer sound similar. I would inspect the sprayer for cracks or blockage. If the water is not flowing evenly you may loose the spinning effect.
Based on your "airplane "description it sounds like you have some wobble in there. Again I would remove and inspect the mechanism and check dishes on both racks to see if one rack cleans better than the other.
Then post a model and more info.

 

[crawdoogie]

Poor cleaning can be caused by the dishwasher not getting enough water. A common cause of this is a bad water-inlet valve. To access the valve you'll need to remove the lower access panel. It's the device with the main water line from the house, a rubber tube to the dishwasher, and two wires attached to it.

When a water-inlet valve goes bad, you may hear what plumber's call "water hammer." This could be the "airplane taking off" sound that you are hearing (excellent description by the way!) If the water-inlet valve is defective, you need to completely replace it.
Good info on this here:

http://www.repairclinic.com/0088_9_1.asp#Level1_2

Doug

PS: I have a Frigidare DW and it has never cleaned well!