Perhaps our lack of inner peace is due to some extent to the effect of noise upon the nervous system of modern people. Scientific experiments show that noise in the place where we work, live, or sleep reduces efficiency to a noticeable degree. Contrary to popular belief, it is doubtful if we ever completely adjust our physical, mental, or nervous mechanisms to noise. No matter how familiar a repeated sound becomes, it never passes unheard by the subconscious. Automobile horns, the roar of airplanes, and other strident noises actually result in physical activity during sleep. Impulses transmitted to and through the nerves by these sounds cause muscular movements which detract from real rest. If the reaction is sufficiently severe, it partakes of the nature of shock.