Mr. Mitchell says GM has devoted considerable resources to reducing unwanted vibrations and noise in automobiles. Fluid-filled engine mounts, developed eight years ago, are an example of a simple device that eliminates noise by reducing the transfer of vibrations from the engine to the frame of the car. Like double-wall, insulated exhause pipes and sound absorbers in the headliner. We devote a lot of energy to reducing noise, because customers tell us it's one of the best mechanisms they have for assessing quality. Reducing noise can get kind of tricky.
Nobody wants road noise, thus tire makers have sound standards to meet.
On the other hand, nobody wants absolute silence. They want some feedback that the engine is there. The key to the noise-cancellation feature of DSP systems rests in the software that's built into the chips. That's where most research and development energies are being expended. The chip has to be told which sounds to attack and which to leave alone.