Ever so often when I start my 94gt there is a very loud roaring noise coming from the speakers. No radio sounds, only the roaring. Previous owner installed an aftermarket radio and the only way I can get the sound to quit is remove the removable face plate. I can reinstall the faceplate at a later date and the radio will be normal. The noise never comes on while I am driving. Only at start up. The noise is so loud that it would be undrivable without taking the faceplate off the radio. I believe it is coming from all the speakers. This happens about once ever 2-3 months, not ever time I drive it. I haven't looked for loose grounds and would like a heads up on where to start. It has the amp thing in the trunk under the rear deck.