**4. Combining the traditional and contemporary approach**

When considering only noise barriers as an instrument to combat noise and noise pollution, they have the ability to reduce noise levels by 3–20 dB. Over 3000 km of noise barriers have been installed alongside European rail networks. They are even more widely used alongside roads, including countries such as Austria, Denmark, France, Germany, Italy, Poland, Spain and Netherlands. Keeping that in mind, it can be concluded that noise barriers as a solution are mainly focused on reducing the noise levels from traffic sources, while the goal of the WHO and many researchers is to improve the overall quality of life by using different tools, guidelines, descriptors and an interdisciplinary approach by designing, preserving and investigating positively perceived soundscapes as previously mentioned.

For each noise barrier, its acoustic performance can be determined, as described in Section 2.1. Noise levels reduction with noise barriers. Here are some practical examples regarding the different performance of several noise barriers:


different types of barriers was conducted using acoustic simulation software Enpro (Environment Noise Prediction and Design Program). Predicted insertion loss data is shown **Table 4**.

• In [42] a comparison of the obtained values for the green wall sound absorption coefficient and different common building materials was carried out (**Figure 14**).

In addition, for each type of noise barrier, its visual stimulus can be determined by using soundscape research which is described in [41] where images of five types of noise barriers were investigated. In the aforementioned research, timber, metal, transparent glass, vegetation and concrete barriers were created using Adobe Photoshop CS4 software. A viewpoint was fixed in order to avoid influence of view angles. Furthermore, small and large portion of ivy images were covered on the transparent and concrete barriers images in order to evaluate the visual effect of vegetation.

Furthermore, in [43] a case study is presented, where a sample of residents living close to a railway line assessed noise-related aspects for several barriers with different visual characteristics in an IVR laboratory test. In particular, three main factors were analysed: the barrier type concerning the visibility of the noise source through the screen, the visual aspect of the barrier concerning some aesthetic

**Figure 13.** *Parameter of average noise reduction (*ILavg*) depending on the receiving position [40].*


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level increased.

**Figure 14.**

that type of noise barriers.

**5. Conclusions**

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

issues and the noise level at the receiver concerning the acoustic performance of the barrier and the magnitude of the sound source. The main results of the ANOVA analysis showed that for transparent barriers, perceived loudness and noise annoyance were judged lower than for opaque barriers; this difference increased as noise

*Comparison of sound absorption coefficient for the green wall and common building materials.*

A much more effective way of reducing noise and noise pollution is to use noise barriers and soundscape together, by incorporating noise barriers, auditory ratings and visual assessment. Here we note that this way allows the design of better noise barriers and soundscapes and thus better acoustic urban environments. It has been proven that a noise barrier that better attenuates low frequencies such as a concrete noise barrier has a better acoustic rating. When considering user ratings, it has been proven in [41] that people respond much better to noise barriers made from natural materials and especially green walls, i.e. the visual pleasantness is much higher for

To sum it up, the best way to tackle this burning issue, i.e. noise pollution, is the combination of both methods (noise barriers and soundscape research). Both methods complement each other in a very good and effective way while moving and

In this chapter two different approaches for noise reduction have been described and discussed in detail. Finally, by comparing these approaches, it can be concluded

that each one of them has its advantages, disadvantages and limitations. The final choice of noise reduction measure in most cases depends on the limitations regarding the location, cost, etc. It can be concluded that the best results regarding the reduction of noise pollution can be obtained by combining both described

in a way breaking the limitations which each individual method has.

#### **Table 4.**

*Predicted insertion loss data [41].*

*Noise and Environment*

(**Figure 14**).

tion loss data is shown **Table 4**.

different types of barriers was conducted using acoustic simulation software Enpro (Environment Noise Prediction and Design Program). Predicted inser-

• In [42] a comparison of the obtained values for the green wall sound absorption coefficient and different common building materials was carried out

In addition, for each type of noise barrier, its visual stimulus can be determined by using soundscape research which is described in [41] where images of five types of noise barriers were investigated. In the aforementioned research, timber, metal, transparent glass, vegetation and concrete barriers were created using Adobe Photoshop CS4 software. A viewpoint was fixed in order to avoid influence of view angles. Furthermore, small and large portion of ivy images were covered on the transparent and concrete barriers images in order to evaluate the visual effect of vegetation. Furthermore, in [43] a case study is presented, where a sample of residents living close to a railway line assessed noise-related aspects for several barriers with different visual characteristics in an IVR laboratory test. In particular, three main factors were analysed: the barrier type concerning the visibility of the noise source through the screen, the visual aspect of the barrier concerning some aesthetic

**Frequency (Hz) 63 125 250 500 1 k 2 k 4 k 8 k** Timber 2.0 2.5 9.7 13.1 15.9 17.9 18.0 18.0 Metal 2.2 7.7 16.6 19.0 19.6 18.9 19.0 18.7 Transparent 2.0 3.4 7.8 12.7 14.7 14.9 15.4 15.7 Concrete 14.7 14.4 17.7 19.0 19.6 19.9 20.0 20.0 Vegetation 6.3 7.3 12.3 17.0 18.6 18.9 19.3 18.0

*Parameter of average noise reduction (*ILavg*) depending on the receiving position [40].*

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**Table 4.**

**Figure 13.**

*Predicted insertion loss data [41].*

**Figure 14.** *Comparison of sound absorption coefficient for the green wall and common building materials.*

issues and the noise level at the receiver concerning the acoustic performance of the barrier and the magnitude of the sound source. The main results of the ANOVA analysis showed that for transparent barriers, perceived loudness and noise annoyance were judged lower than for opaque barriers; this difference increased as noise level increased.

A much more effective way of reducing noise and noise pollution is to use noise barriers and soundscape together, by incorporating noise barriers, auditory ratings and visual assessment. Here we note that this way allows the design of better noise barriers and soundscapes and thus better acoustic urban environments. It has been proven that a noise barrier that better attenuates low frequencies such as a concrete noise barrier has a better acoustic rating. When considering user ratings, it has been proven in [41] that people respond much better to noise barriers made from natural materials and especially green walls, i.e. the visual pleasantness is much higher for that type of noise barriers.

To sum it up, the best way to tackle this burning issue, i.e. noise pollution, is the combination of both methods (noise barriers and soundscape research). Both methods complement each other in a very good and effective way while moving and in a way breaking the limitations which each individual method has.
