There's no reason why a microphone and an accelerometer would be hard to connect as input features. The car can make use of the same hints, and most probably make better use than even humans by learning to distinguish more informative patterns.
When we were designing our vehicle for the 2004 DARPA Grand Challenge, we considered installing a guitar pickup on the frame to sense vibration. Early plans for the Grand Challenge involved more off-road driving, and we wanted something to give us a sense of surface roughness. In practice, the off-road aspect wasn't important and we were overdesigned in that area. We had a 6-wheel drive vehicle and a windshield washer/compressed air cleaning system for the sensors, which were totally unnecessary.
