**2. A traditional approach: noise barriers**

In order to reduce noise pollution, different protection measures can be applied. In terms of traffic noise pollution, reducing the impact of traffic noise on both

people and the environments can be achieved by planning and integrating the traffic routes outside the residential areas. In case of existing traffic routes within the residential areas, a good solution for reducing the noise levels is noise barriers [1–3]. Here we note that the noise barrier efficiency depends principally on their design. In the field of noise barriers, it is already established that the most favourable noise barriers are those which have a diffuse element on the top. In addition, the diffuse element can be circular, is Y or T shaped and is usually added on the top of the plain barrier. In particular, the Y and T shapes have proven to be a very good choice for the shape of the diffuse elements [4–7]. Ishizuka and Fujiware [4] gave an extensive overview of the acoustic efficiency for several typical diffuse element forms placed at the top of the noise barrier. **Figure 1** shows a plane (reference) noise barrier and several other noise barrier types obtained by adding capes at the top of noise barriers bearing in mind that the caps are made of different materials [4]. The optimization of T-shape noise barriers was more thoroughly studied by Baulac et al. [5] and Monazam and Lam [6], while Grainer et al. [7] explored the Y-shape noise barrier optimization.

In Toledo et al. [8] a procedure was proposed for improving the acoustic efficiency of noise barriers using top-edge devices. Furthermore, in Toledo et al. [9] a procedure was developed for the optimization of well-based designs on the top of road barriers with both thick and very thin bodies by coupling a genetic algorithm with a 2D Dual BEM code. In addition, when placing a noise barrier in residential areas, studies have shown that it is also essential to keep in mind the "visual pleasantness" of the noise barrier which is the parameter introduced in Maffei et al. [10, 11].

Grubeša et al. [12, 13] have addressed the problem of economic feasibility of building noise barriers of various shapes and materials. Research and calculations done in this paper suggest a new specific noise barrier cost parameter (Ke) that must be taken into account during the optimization process of noise barrier shapes and materials while using computational calculations and optimization methods.

**53**

*Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056*

**2.1 Noise level reduction with noise barriers**

comparison of different noise barrier performances:

frequency dependent.

**2.2 Noise barrier types**

• Panel, shown in **Figure 2**.

There are three basic parameters which describe noise barriers: insertion loss (IL), transmission losses (TL) and barrier absorption coefficient. Noise barriers can be defined as a certain sound "obstacle" between the sound source and the observer, i.e. the sound propagates around and over noise barriers. However, in real-case scenarios, the sound propagates also through the noise barrier, which is usually neglected, i.e. the sound proportion passing through the barrier is substantially smaller than the sound proportion which will cross over and around the noise barrier. The noise level reduction achieved by the installation of noise barriers is often called an additional noise level reduction, since the noise level will be primarily reduced due to the distance from the source and the air absorption and furthermore because the noise barrier itself. When quantifying noise reduction, a parameter, entered losses, is also often used and is defined as the noise level reduction arisen from the installation of noise barrier (insertion loss). It represents the difference between the sound pressures *pp* and *pn*, which are measured at the observer location before and after the noise barrier is placed, with the same ground configuration and position of the source and receiver, calculated according to the expression in Eq. (1). This parameter is usually used for

> æ ö = - ç ÷ ç ÷ è ø 20 *<sup>p</sup>*

The noise reduction parameter which arises from the installation of the noise barrier depends on the shape and material of the noise barrier, the frequency and type of sound source, the position of the noise barrier with respect to the source and the observer and the absorption properties of the soil on both sides of the noise barrier. The noise barrier effectiveness directly depends on the frequency of the sound propagating over it, and therefore the parameter insertion loss (IL) is also

The noise barrier sound-absorbing properties are qualified according to EN 1793-1 [14], while the airborne sound insulation index which corresponds to the

There are three basic types of noise barriers. These are ground-mounted noise barriers, structure-mounted noise barriers and a combination of the first two types. Ground-mounted noise barriers are constructed of natural earth materials such as earth, stone, rocks or gravel. This type of noise barriers is typically constructed from excess materials in a noise-protected location, and source and availability of such natural materials are factors that can significantly affect the cost of such noise protection. Ground-mounted noise barriers take up more space than structuremounted noise barriers. The reason for this is the slope of the embankment, which must gradually increase in order to maintain the stability of the whole structure. The increase is defined by the ratio *m*:*n*, where m is growth in the horizontal direction and n is growth in the vertical direction. For most embankments, the ratio is 2:1

Structure-mounted noise barriers or commonly called just noise barriers can be:

transmitted noise barrier losses is defined in EN 1793-2 [15].

or 1.5:1, while for stone embankments, the increase is usually 1:1.

• Brick and masonry, shown in **Figure 3** [16].

*<sup>p</sup> IL log log*

*n*

(1)

*p*

**Figure 1.** *Different types of noise barriers [4].*

*Noise and Environment*

barrier optimization.

Maffei et al. [10, 11].

methods.

people and the environments can be achieved by planning and integrating the traffic routes outside the residential areas. In case of existing traffic routes within the residential areas, a good solution for reducing the noise levels is noise barriers [1–3]. Here we note that the noise barrier efficiency depends principally on their design. In the field of noise barriers, it is already established that the most favourable noise barriers are those which have a diffuse element on the top. In addition, the diffuse element can be circular, is Y or T shaped and is usually added on the top of the plain barrier. In particular, the Y and T shapes have proven to be a very good choice for the shape of the diffuse elements [4–7]. Ishizuka and Fujiware [4] gave an extensive overview of the acoustic efficiency for several typical diffuse element forms placed at the top of the noise barrier. **Figure 1** shows a plane (reference) noise barrier and several other noise barrier types obtained by adding capes at the top of noise barriers bearing in mind that the caps are made of different materials [4]. The optimization of T-shape noise barriers was more thoroughly studied by Baulac et al. [5] and Monazam and Lam [6], while Grainer et al. [7] explored the Y-shape noise

In Toledo et al. [8] a procedure was proposed for improving the acoustic efficiency of noise barriers using top-edge devices. Furthermore, in Toledo et al. [9] a procedure was developed for the optimization of well-based designs on the top of road barriers with both thick and very thin bodies by coupling a genetic algorithm with a 2D Dual BEM code. In addition, when placing a noise barrier in residential areas, studies have shown that it is also essential to keep in mind the "visual pleasantness" of the noise barrier which is the parameter introduced in

Grubeša et al. [12, 13] have addressed the problem of economic feasibility of building noise barriers of various shapes and materials. Research and calculations done in this paper suggest a new specific noise barrier cost parameter (Ke) that must be taken into account during the optimization process of noise barrier shapes and materials while using computational calculations and optimization

**52**

**Figure 1.**

*Different types of noise barriers [4].*

## **2.1 Noise level reduction with noise barriers**

There are three basic parameters which describe noise barriers: insertion loss (IL), transmission losses (TL) and barrier absorption coefficient. Noise barriers can be defined as a certain sound "obstacle" between the sound source and the observer, i.e. the sound propagates around and over noise barriers. However, in real-case scenarios, the sound propagates also through the noise barrier, which is usually neglected, i.e. the sound proportion passing through the barrier is substantially smaller than the sound proportion which will cross over and around the noise barrier. The noise level reduction achieved by the installation of noise barriers is often called an additional noise level reduction, since the noise level will be primarily reduced due to the distance from the source and the air absorption and furthermore because the noise barrier itself. When quantifying noise reduction, a parameter, entered losses, is also often used and is defined as the noise level reduction arisen from the installation of noise barrier (insertion loss). It represents the difference between the sound pressures *pp* and *pn*, which are measured at the observer location before and after the noise barrier is placed, with the same ground configuration and position of the source and receiver, calculated according to the expression in Eq. (1). This parameter is usually used for comparison of different noise barrier performances:

$$\text{HL} = -20 \log \log \left( \frac{p\_v}{p\_u} \right) \tag{1}$$

The noise reduction parameter which arises from the installation of the noise barrier depends on the shape and material of the noise barrier, the frequency and type of sound source, the position of the noise barrier with respect to the source and the observer and the absorption properties of the soil on both sides of the noise barrier. The noise barrier effectiveness directly depends on the frequency of the sound propagating over it, and therefore the parameter insertion loss (IL) is also frequency dependent.

The noise barrier sound-absorbing properties are qualified according to EN 1793-1 [14], while the airborne sound insulation index which corresponds to the transmitted noise barrier losses is defined in EN 1793-2 [15].

#### **2.2 Noise barrier types**

There are three basic types of noise barriers. These are ground-mounted noise barriers, structure-mounted noise barriers and a combination of the first two types. Ground-mounted noise barriers are constructed of natural earth materials such as earth, stone, rocks or gravel. This type of noise barriers is typically constructed from excess materials in a noise-protected location, and source and availability of such natural materials are factors that can significantly affect the cost of such noise protection. Ground-mounted noise barriers take up more space than structuremounted noise barriers. The reason for this is the slope of the embankment, which must gradually increase in order to maintain the stability of the whole structure. The increase is defined by the ratio *m*:*n*, where m is growth in the horizontal direction and n is growth in the vertical direction. For most embankments, the ratio is 2:1 or 1.5:1, while for stone embankments, the increase is usually 1:1.

Structure-mounted noise barriers or commonly called just noise barriers can be:


**Figure 2.** *Panel noise barriers.*

**55**

**Figure 5.**

*Precast concrete noise barriers.*

**Figure 4.**

*Cast-in place noise barriers.*

*Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056*

• Freestanding which can be:

*2.2.1 Panel noise barriers*

○ Cast concrete at the installation site, shown in **Figure 4** [16].

and positioned at the installation site, shown in **Figure 5**.

○ Green vertical gardens, shown in **Figure 6**.

○ Concrete blocks manufactured under controlled conditions then delivered

Panel noise barriers usually consist of a board or panel, which can be wooden, metal or concrete, and it can be constructed out of one piece, or it can be assembled at the place of noise barrier installation from several components. The panels are

**Figure 3.** *Brick and masonry noise barriers.*

*Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056*

	- Cast concrete at the installation site, shown in **Figure 4** [16].
	- Concrete blocks manufactured under controlled conditions then delivered and positioned at the installation site, shown in **Figure 5**.
	- Green vertical gardens, shown in **Figure 6**.

*Noise and Environment*

**54**

**Figure 3.**

**Figure 2.** *Panel noise barriers.*

*Brick and masonry noise barriers.*

Panel noise barriers usually consist of a board or panel, which can be wooden, metal or concrete, and it can be constructed out of one piece, or it can be assembled at the place of noise barrier installation from several components. The panels are

**Figure 4.** *Cast-in place noise barriers.*

**Figure 5.** *Precast concrete noise barriers.*

**Figure 6.** *Green vertical noise barriers.*

mounted between the base posts. The basic elements of this noise barrier type are the post and the elements which attach it to the foundation, the panels and the elements which attach the panels to the posts.

There are several ways to set up or build a foundation for posts:

