Transportation Noise

Motor vehicles and aircraft are estimated to cause more urban and community noise than all other sources combined, and 60 to 70% of the U.S. population lives in locations where such transportation noise is a problem. The number of workers exposed to hazardous noise in their daily work is estimated at between 5 and 15% of the population; most of them are also exposed to the annoying, sleep-destroying general urban noise.

Table 6.2.4 lists some typical values for aircraft, motor vehicles, railways, and subways. These values are not the absolute maximum but high typical values; actual noise levels for motor vehicles, for example, are modified by the condition of the vehicle, condition of the pavement, manner of driving, tires, and surroundings. Both motor vehicles and aircraft are directional sources in that the location of the point of measurement affects the measured noise-level values.

Of all sources, aircraft noise probably causes the most annoyance to the greatest number of people. Airports are located near population centers, and approach and takeoff paths lie above residential areas. Residential buildings are especially vulnerable to aircraft noise since it comes from above striking roofs and windows, which are usually vulnerable to noise penetration. The individual resident feels that he is pursued by tormenting noise against which he has no protection and no useful channel for protest.

Railway equipment has a high noise output but causes less annoyance than either highway and street traffic or air traffic. Railway noise is confined to areas adjacent to right-of-way, usually comes from extended sources, and is predictable. It is basically low frequency, thus less annoying than aircraft. Since railway equipment stays on its established routes, protection to residential areas is easily provided. Subway trains can be extremely annoying to their passengers; their noise levels are high; tunnel and station surfaces are highly reflective; and many passengers are present. Newer subway construction is less noisy than in the past (when 100 to 110 dBA was common). Subways, trolleys, and city buses all contribute considerably to urban noise and vibration.

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