**2.1 Road traffic noise**

Road traffic noise depends on the following three factors:

• Type of road vehicles.


When considering vehicles that have an internal combustion engine (ICE) as the noise source, most of the noise comes from the sources or systems shown in **Figure 2**. The aforementioned sources and systems are explained in detail in the following paragraph.

Engine noise is created during the process of compression and expansion in the engine, which creates engine vibrations which then emit noise. The engine noise depends on the engine volume, speed, and capacity. The suction system noise is caused by the opening and closing of the suction valves, and furthermore the intensity of such noise depends on the mode of operation of the engine, the speed of the engine itself, and the type of air filter. Noise from the exhaust system is created by the sudden release of gas into the exhaust system itself in order to open the exhaust valve. The fan noise is generated due to the operation of the fans in the vehicle, and the fans generally produce a broadband noise. Tire noise occurs when the tires and

#### **Figure 1.**

*Distribution of human noise annoyance according to the type of noise source [1].*


#### **Table 1.**

*The average noise level generated by different types of vehicles (International Union of Railways (UIC)).*

**77**

**Figure 3.** *Electric vehicle.*

**Figure 2.**

*Noise sources in a vehicle.*

*Traffic Noise*

*DOI: http://dx.doi.org/10.5772/intechopen.92892*

road surfaces come into contact. This type of noise depends on the type of road surface, the tire construction, and finally the speed and driving style [2].

In terms of noise pollution, electric vehicles represent the future, especially when compared to vehicles with an internal combustion engine (see **Figure 3**). However, at low speeds, electric vehicles produce very small levels of noise, i.e., in current acoustic urban environments, they are practically inaudible. For example, the noise level difference between an electric vehicle and an internal combustion

### *Traffic Noise DOI: http://dx.doi.org/10.5772/intechopen.92892*

*Noise and Environment*

following paragraph.

• Friction between the vehicle wheels and the road surface.

*Distribution of human noise annoyance according to the type of noise source [1].*

**Type of vehicle Average noise level [dBA]**

*The average noise level generated by different types of vehicles (International Union of Railways (UIC)).*

Motorcycle 90 Heavy cargo truck 103 Turbojet airplane 150 Fast passenger train 65 Cargo train (speed up to 120 km/h) 60 Local train 70

) 82

When considering vehicles that have an internal combustion engine (ICE) as the noise source, most of the noise comes from the sources or systems shown in **Figure 2**. The aforementioned sources and systems are explained in detail in the

Engine noise is created during the process of compression and expansion in the engine, which creates engine vibrations which then emit noise. The engine noise depends on the engine volume, speed, and capacity. The suction system noise is caused by the opening and closing of the suction valves, and furthermore the intensity of such noise depends on the mode of operation of the engine, the speed of the engine itself, and the type of air filter. Noise from the exhaust system is created by the sudden release of gas into the exhaust system itself in order to open the exhaust valve. The fan noise is generated due to the operation of the fans in the vehicle, and the fans generally produce a broadband noise. Tire noise occurs when the tires and

• Driving style and driver behavior.

**76**

**Table 1.**

**Figure 1.**

Car (700–1300 cm3

road surfaces come into contact. This type of noise depends on the type of road surface, the tire construction, and finally the speed and driving style [2].

In terms of noise pollution, electric vehicles represent the future, especially when compared to vehicles with an internal combustion engine (see **Figure 3**). However, at low speeds, electric vehicles produce very small levels of noise, i.e., in current acoustic urban environments, they are practically inaudible. For example, the noise level difference between an electric vehicle and an internal combustion

**Figure 2.** *Noise sources in a vehicle.*

**Figure 3.** *Electric vehicle.*

engine (ICE) vehicle can be greater than 6 dB (A) at 10 km/h. Unfortunately, much later at higher speeds, both types of car become equally loud, mainly due to tire noise.

When considering how traffic flow affects the subjective perception of noise levels, it can be concluded that it depends on the number of vehicles, their speed, and structure as described in the following paragraph.

A traffic flow of 2000 vehicles per hour produces twice the perceived noise level than 200 vehicles per hour. If the traffic speed is 105 km/h, it produces twice the perceived noise level than the 50 km/h traffic flow. One heavy weight vehicle (HV > 3.5 tons) with a speed of 70 km/h creates a perceived noise level of 28 lightweight vehicles (LV <3.5 tons).
