Road Traffic Noise
Road traffic is the most widespread source of noise in all countries and the most prevalent cause of annoyance and interference. Therefore, traffic noise reduction measures have the highest priority.
Rail Traffic Noise
As with road traffic noise, LAeq is the preferred index for rail traffic noise. In some countries, Rating Levels are calculated from LAeq by subtracting (normally) 5dB, the so-called railway bonus.
In Japan, LASmax is used for the Shinkansen high-speed line. Generally, using maximum levels as the only limit has the disadvantage of disregarding the number of trains.
Assessment is carried out using various reference time intervals depending on country. These intervals range from one 24-hour period to three separate intervals for day, rest and night.
The noise limits for new lines in residential areas vary between 60 and 70dB. In some countries, the railway bonus is included in the limit values.
The railway bonus is based on social surveys from several countries, comparing the annoyance from road and rail traffic. The effect is more pronounced at higher levels.
The most important tool for noise control at airports is noise zoning for land-use, planning and noise insulation programs. Noise from commercial aircraft is only a problem around airports as this is where aircraft converge at low altitude and high engine power.
Increasing air traffic and city expansion will exacerbate the noise problems, while aircraft noise reduction, traffic and flight path restrictions can alleviate them. As a last resort, existing dwellings can be protected against noise by improving windows and roofs.