**3. Case study basic information**

As stated, the case study is based on [1]. The main characteristics of the case are presented in Section 1. In this section, it will be presented in detail.

## **3.1 Sound sources**

There are several sound sources at the industrial plant, related to equipment, transportation, and personnel movement. **Figure 4** illustrates the location of the main sound sources at the plant.

The case study is centered only on the emissions from the main noise source in the industrial plant: the coal processing mill. All the measurements selected to work with are representative of this particular situation, since they were specially chosen, and the absence of other operating sources was checked.

The measurements for characterizing the coal processing mill were taken at 12 m distance. **Table 1** presents a representative spectrum of the source emission SPL, in octave bands. It was obtained by composing five SPL measurements, taken on different days. The obtained values were LAF,eq = 83.4 dB and LCF,eq = 84.9 dB.

#### **3.2 Receivers**

Two receivers will be considered: P1 and P2, defined as monitoring points on the property line. **Figure 5** shows their location in relation to the plant.

*Evaluation of Industrial Noise Reduction Achieved with a Green Barrier: Case Study DOI: http://dx.doi.org/10.5772/intechopen.108835*

#### **Figure 4.**

*Main sound sources (drawing overlapped on GoogleEarth image).*


#### **Table 1.**

*Sound emission spectrum of the coal processing mill at 12 m distance.*

## *3.2.1 Point P1*

Point P1 is located facing southwest of the plant, 813 m from the coal mill. Since it is close to a neighboring house, which is temporarily occupied, it is a very important surveillance point. Our study focuses on the results at this point to assess the acoustic behavior of the green barrier.

The background noise at P1 was determined during the shutdown period of the plant. It resulted in a LAFeq value of 40 dB. Its spectrum is shown in **Table 2**.

**Table 3** presents the measured SPL at P1 when the coal processing mill was the only noise source operating at the plant. The measured SPL were LAF,eq = 47.7 dB and LCF,eq = 54.0 dB.

### *3.2.2 Point P2*

Point P2 is located on the perimeter of the industrial property, with no nearby houses and close to a large external afforestation. It is located facing southeast, 239 m

**Figure 5.** *Relative location of the coal processing mill, P1 and P2 (drawing overlapped on GoogleEarth image).*



#### **Table 3.**

*SPL spectrum measured at P1 when the coal processing mill was the only operating noise source in the plant.*

from the source. Since there are no obstacles between P2 and the coal processing mill, it is the best point to verify the sound depletion law from the source.

The background noise at P2 was also determined during the shutdown period of the plant. LAFeq was 50 dB. The spectrum of background noise at P2 is shown in **Table 4**.

*Evaluation of Industrial Noise Reduction Achieved with a Green Barrier: Case Study DOI: http://dx.doi.org/10.5772/intechopen.108835*


**Table 4.**

*Background noise spectrum at P2.*


#### **Table 5.**

*SPL spectrum measured at P2 when the coal processing mill was the only operating noise source in the plant.*

**Table 5** presents the measured SPL at P2 when the coal processing mill was the only noise source operating at the plant. The measured SPL were LAF,eq = 62.5 dB and LCF,eq = 68.9 dB.
