**2.3 Aircraft traffic noise**

Aircraft traffic also causes several environmental problems or in other words an increase of noise. Nowadays, when observing the rapid development of all types of traffic, especially aircraft traffic, it can be concluded that there has been a significant increase in noise levels. In particular, the population living near airports is affected by the negative effects of noise exposure.

Aircraft noise can be divided into groups, which are shown in **Figure 5**:


The noise sources generated by the engine groups are:


**Figure 4.** *Significant noise sources in the case of the high-speed train.*

#### **Figure 5.** *Significant aircraft noise sources.*

The noise produced by a turbojet engine can be divided into following groups:


Turbojet engine noise presented a big problem in the 1960s, especially the intake noise of this type of engine. The noise source of such intake noise is the compressor blades. During time as technology has evolved, aircrafts have become quieter, and therefore noise reduction in that sense continues even today.

The turbofan engine was designed to reduce aviation noise levels. In the case of the first turbofan engines, the largest noise source was the compressor, turbine, and jet exhaust. Newer turbofan engine models have succeeded to reduce the aforementioned noise levels. Turbofan engine consists of blades and a turbojet engine. This type of engine is often used in commercial aircraft industry.

Aircraft structure noise is defined as the sound which is produced from the movement of air between a solid body and air. The largest "manufacturers" of aircraft structure noise are landing gear, aircraft wings, and the flaps which are shown in **Figures 6** and **7**. The noise generated by these aircraft parts depends on different aircraft configurations.

The noise level of an aircraft takeoff can be compared to the noise level produced by the engine group, while the landing aircraft engine group noise level is almost insignificant.

The noise produced by the flaps is created by the outer edges of the flaps. The main cause of flap noise is the emersion of air vortex which is created by flap extension. This vortex is the main cause of noise at the end of the wings.

**81**

produces the landing gear noise [4].

**2.4 Other types of noise sources**

*Traffic Noise*

**Figure 6.**

**Figure 7.**

*Wing with extended flaps.*

*Aircraft structure noise sources.*

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

Another significant source of aircraft structural noise is landing gear. Landing gear noise is generated during takeoff and landing of an aircraft. During takeoff and landing, the landing gear is lowered; thus high air resistance occurs, which

Other noise sources include industrial noise, noise caused by various construc-

Industrial noise (shown in **Figure 8**) is the amount of acoustic energy received by the human hearing system while working at the industrial hall. Occupational noise or industrial noise is a common term used when it comes to occupational

tion work, and noise produced by different music and sports events.

*Noise and Environment*

• Compressor noise.

*Significant aircraft noise sources.*

**Figure 5.**

• Output jet noise.

aircraft configurations.

almost insignificant.

• Vibration-induced noise.

The noise produced by a turbojet engine can be divided into following groups:

Turbojet engine noise presented a big problem in the 1960s, especially the intake noise of this type of engine. The noise source of such intake noise is the compressor blades. During time as technology has evolved, aircrafts have become quieter, and

The turbofan engine was designed to reduce aviation noise levels. In the case of the first turbofan engines, the largest noise source was the compressor, turbine, and jet exhaust. Newer turbofan engine models have succeeded to reduce the aforementioned noise levels. Turbofan engine consists of blades and a turbojet engine. This

Aircraft structure noise is defined as the sound which is produced from the movement of air between a solid body and air. The largest "manufacturers" of aircraft structure noise are landing gear, aircraft wings, and the flaps which are shown in **Figures 6** and **7**. The noise generated by these aircraft parts depends on different

The noise level of an aircraft takeoff can be compared to the noise level produced by the engine group, while the landing aircraft engine group noise level is

The noise produced by the flaps is created by the outer edges of the flaps. The main cause of flap noise is the emersion of air vortex which is created by flap exten-

therefore noise reduction in that sense continues even today.

type of engine is often used in commercial aircraft industry.

sion. This vortex is the main cause of noise at the end of the wings.

**80**

**Figure 6.** *Aircraft structure noise sources.*

**Figure 7.** *Wing with extended flaps.*

Another significant source of aircraft structural noise is landing gear. Landing gear noise is generated during takeoff and landing of an aircraft. During takeoff and landing, the landing gear is lowered; thus high air resistance occurs, which produces the landing gear noise [4].
