Chapter 5 presents a detailed description of the characterization and measurement of exterior noise including both fixed and moving sources as well as various environmental noises. These include traffic noise, railway noise, and aircraft noise. Various noise barriers are discussed, describing materials and practical constraints. The chapter further discusses noise propagation including the effects of distance, air attenuation, barrier attenuation, attenuation due to ground cover and grazing, focusing, refraction effects, and airport noise contours.