Noise Pollution man-made noise harmful to health or welfare. Transportation vehicles are the worst offenders, with aircraft, railroad stock, trucks, buses, automobiles, and motorcycles all producing excessive noise. Noise intensity is measured in decibel (dB) units. Subject to 45 dB of noise, the average person cannot sleep. At 120 dB the ear registers pain; hearing damage begins at a much lower level, about 85 dB.