Abstract
KEYWORDS:
Noise; Pollution; Vehicle; Measurement; Sound.
ABSTRACT:
Traffic noise is probably the most serious and pervasive type of noise pollution. Studies have shown that on a daily basis almost 40 % of population is exposed to undesirable levels of traffic noise and a further 10 % is exposed to excessive levels. Traffic noise has become a serious problem now because of inadequate urban planning in the past. Homes, schools, hospitals, churches, libraries and other community buildings were routinely built on main roads without buffer zones or adequate soundproofing. The problem has been compounded by increases in traffic volumes far beyond the expectations of our early urban planners. At low speeds, most traffic noise is caused by vehicle engines, transmissions, exhausts and brakes. The stop-start braking and acceleration during peak-hour congestion also increases noise levels. On freeways where speeds are high and relatively constant, most noise is caused by a combination of tire contact with the road and aerodynamic drag over the vehicle. We studied the vehicle noise pollution in urban and rural areas, on various kind of road vehicles (buses, trolley buses, trams, cars). The annual medium levels of day noise pollution in the residences on the main streets in Brasov, frequently pass over the 70 dB limit. The average sound levels emitted by vehicles traveling at 50-60 km/h in a 12-15 m road (no. vehicles per hour / sound level): 100 v/h (~63dB), 500 v/h (~70dB), 1000 v/h (~73dB), 2000 v/h (~76dB). The vehicle noise was measured with the noise analyzer Bruel&Kjaer 2237 Controller. Some solutions of noise reducing are: reducing engine and gearbox noise; reducing air drag; reducing tyre/road contact noise.