Broadly, "everything is the same, nothing attracts attention except a noise as loud as a thunderclap." I agree with Michael. This a long sentence that is written in strictly correct grammar, with a precisely meaning--yet very badly written. Here is my "translation:"
"Many jobs force a worker to use one set of muscles endlessly, in one monotonous pattern, like a robot. People forced to do robotic work will tend to lead robotic lives. Nothing will seem different or unusual to them, unless it hits them like a bolt of lightning."