International Journal of Occupational Safety and Ergonomics
ISSN: 1080-3548 (Print) 2376-9130 (Online) Journal homepage: http://www.tandfonline.com/loi/tose20
Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices Krzysztof Kosała & Bartłomiej Stępień To cite this article: Krzysztof Kosała & Bartłomiej Stępień (2016) Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices, International Journal of Occupational Safety and Ergonomics, 22:1, 92-101, DOI: 10.1080/10803548.2015.1106702 To link to this article: http://dx.doi.org/10.1080/10803548.2015.1106702
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Date: 13 March 2016, At: 09:28
International Journal of Occupational Safety and Ergonomics (JOSE), 2016 Vol. 22, No. 1, 92–101, http://dx.doi.org/10.1080/10803548.2015.1106702
Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices Krzysztof Kosałaa,b∗ and Bartłomiej St˛epie´na
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a AGH
University of Science and Technology, Poland; b Central Institute for Labour Protection – National Research Institute (CIOP-PIB), Poland
This paper presents the verification of two partial indices proposed for the evaluation of continuous and impulse noise pollution in quarries. These indices, together with the sound power of machines index and the noise hazard index at the workstation, are components of the global index of assessment of noise hazard in the working environment of a quarry. This paper shows the results of acoustic tests carried out in an andesite quarry. Noise generated by machines and from performed blasting works was investigated. On the basis of acoustic measurements carried out in real conditions, the sound power levels of machines and the phenomenon of explosion were determined and, based on the results, three-dimensional models of acoustic noise propagation in the quarry were developed. To assess the degree of noise pollution in the area of the quarry, the continuous and impulse noise indices were used. Keywords: noise; machines; quarries; acoustic model; noise evaluation indices
1. Introduction Excess noise in mining, which is one of the noxious agents for health in the workplace, is the cause of occupational diseases and accidents at work. In Poland, there are more than 200 mining companies, employing about 150,000 employees, of whom nearly 20% work in hazardous noise conditions.[1–3] The great importance of this problem is shown in statistics of occupational diseases associated with permanent hearing loss, which indicate that there were 71 such cases in 2010 alone.[1,4] Noise is a noxious agent in surface mining too. In Poland, there are 106 surface mining plants, which employ 15,500 employees. The incidence of occupational disease associated with permanent hearing loss in surface mining in 2004–2009 was 2–7 cases annually.[5] This article concerns noise problems in quarries. Due to the introduction of increasingly modern machinery and equipment, often with increasingly larger size and thus higher power, noise exposure is high. In Poland, in 2009, 93 quarries operated with 2873 people employed.[5] In the technological processes of quarries, the machinery and large-scale equipment used are characterized by high efficiency and also by high emission of acoustic energy. In small- and medium-sized quarries, the noisiest machines are mobile crushers, presenting the greatest risk to workers who operate them. In large plants, however, problems are also connected with stationary crushing machines, located in the production line at high altitudes,
*Corresponding author: Email: [email protected]. © 2016 Central Institute for Labour Protection – National Research Institute (CIOP-PIB)
so the noise is spread in a quarry space at longer distances, thereby threatening all workers in the quarry. An analysis of noise originating from machines and equipment involved in the processing of aggregates showed high values of equivalent A-weighted sound pressure level (LAeq ) at workstations, often in excess of 85 dB(A).[6–9] The study of noise sources on large machines of the crusher-sieve type uses a method of inversion,[10–12] with which it is possible to identify acoustic parameters of substitute sources of sound in the machine or in a team of cooperating machines. The other source of noise in quarries is carried out under the blasting process. Despite the short duration of the detonation of explosives (1–3 s), the phenomenon is accompanied by very high sound levels (peak levels of sound pressure exceed 100 dB).[13–15] This type of noise can be a threat to the health of the quarry workers, local residents and, because of the dominant low-frequency components in the spectrum, a threat to the construction of buildings and objects in the plant and its surrounding area. The main objective of several years of research is to develop innovative methods to assess the noise hazard in the working environment in quarries. The method is based on the single number global index,[16] which is the approximate general measure and the function of four partial indices: the noise hazard index at the workstation, sound power of the machines index, continuous noise index and impulse noise index.
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Verification of the last two indices using the example of a selected andesite quarry is presented in this paper. Determination of the value of these indices requires the development of spatial acoustic models of the quarry, which were used in the context of simulation. Acoustic models are based on the acoustic measurements of the phenomena of blasting and working machines conducted in real conditions. Ultimately, the index method is to be used as a helpful tool in shaping the acoustic climate of a quarry in the context of sustainable development issues.
2.
The investigation methodology of noise pollution in an andesite quarry
2.1. Acoustic tests The methods for determining the sound power levels were based on Standard No. ISO 3746:2010.[17] Depending on the existing conditions, various deviations from the requirements of this standard were made, mostly with the measurement points located above the source of noise and/or points located from the side of other sources of high noise levels being abandoned, or when there was no physical space for the location of the measurement point. The sound pressure level was analysed in the one-thirdoctave bands on the surface surrounding the source, which is either a hemisphere or a cube, depending on the shape of the object and on the conditions in the surrounding space. Measurements of LAeq on the premises of working machinery and equipment are based on the current reference method,[18] whereas the level of exposure to noise from blasting was measured in accordance with Standard No. ISO 10843:1997 [19] at the measurement points P1–P3 (Figure 3). Measurements were made with a SVAN 945 and a SVAN 945A (SVANTEK, Poland) equipped with SV type preamps and ½ inch free-field 40AN microphones from G.R.A.S. The status and schedule of work of each piece of machinery and equipment were recorded and used to develop the acoustic model of the quarry.
2.2. Simulation tests A numerical model for theandesite quarry was developed. All noise sources involved in the manufacturing process carried out by this quarry and located in its area were modelled (Figure 1). In the quarry area, there are stationary noise sources that work on shifts 1 and 2 as well as the impulse noise source (blasting works) occurring periodically. On the basis of elevation map provided by the andesite quarry and the documentation prepared during the visits, a numerical model was developed.
Figure 1. Arrangement of machinery and equipment involved in the process of excavation of andesite. Note: 1 = crusher 1; 2 = siever 1; 3 = vibrating feeder; 4 = wheel conveyor; 5 = conveyor 1; 6 = crusher 2; 7 = siever 2; 8 = crusher 3; 9 = conveyor 2; 10 = siever 3; 11 = siever 4; 12 = dispenser aggregate for the loading silo.
The following assumptions were adopted to build the numerical model: • the model takes into account the digital ground model, • the model takes into account buildings fixed to the ground, additional storeys and woodlots, • all items have a real height. In the final stage of building a model for all types: screening, attenuation and noise sources integration of non acoustic data with acoustic data were carried out. In this way, it was possible to obtain a complete acoustical model of the quarry on the basis of which the A-weighted sound pressure level distributions in its area were calculated. SoundPlan software was used for modelling and mapping. This software allows users to perform calculations based on algorithms recommended in the EU Directive on Environmental Noise 2002/49/EC,[20] taking into account the recommendations contained in Standards No. ISO 13474:2009,[21] ISO 9613-1:1993 [22] and ISO 96132:1996.[23] The developed model was calibrated on the basis of measurement results recorded on September 19–20, 2013. 2.3. Indices of noise pollution in the quarry 2.3.1. Continuous noise index WHC The WHC continuous noise index indicates the status of noise pollution, occurring in a given area of the quarry, originating from plant and equipment involved in the process. Machines used in quarries produce more and more power, including: crushers, sievers, loaders, belt conveyors, stackers, trucks and hammers, and also work in an open space often without adequate noise protection. High
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levels of the sound power of machines (usually in excess of 100 dB(A) (Lw(A) )) are a threat not only locally, in the immediate proximity of the employees operating the machines, but also globally – negatively affecting the climate acoustic environment and posing a threat to other workers. To assess the degree of noise pollution in the quarry, the continuous noise index is proposed and is defined by the equation:[16] 6 κ · S0i , (1) WHC = i=1 S0 where S 0 = the assessed area of the quarry (m2 ), S 0i = the area of the quarry under the curve of equal sound levels of < 65, 65, 70, 75, 80, 85 dB(A) (i = 1, . . . , 6 with curves < 65,65, . . . , 85 dB(A)), (m2 ), κ ratio of hazard from continuous noise, defined by Equation (2): κ=
100.1(LAeq −65) 100.1(85−65)
,
(2)
where LAeq = equivalent A-weighted sound pressure level (dB(A)). Equation (1) is based on the assumption of the permissible value of LAeq , which it is assumed, should not exceed 85 dB(A) during an 8-h work day.[24] To determine the values of WHC it is necessary to establish the distribution of values of LAeq on the assessed area of the quarry. For this purpose, one can use an acoustic model of a quarry that may be developed based on the known sound power levels of sources which are used in plant machines and equipment. The WHC index takes values from 0 to 1. The value WHC = 0 is a good acoustic climate in a given quarry. The impact of continuous noise is then insignificant. The value of WHC = 1 indicates the harmful effects of continuous noise. 2.3.2.
Impulse noise index WHI
In addition to work related to the formation of continuous noise in quarries, blasting is used and is a source of impulse noise, negatively affecting both the external environment [25] and the working environment, which is the area of the quarry. Blasting works are accompanied by high sound pressure levels that may pose a threat to the health of quarry workers. Impulse noise occurring at the workstation in industrial plants is the scope of study and analysis of many researchers. Publications from Coles,[26] Sułkowski and ˙ ˙ Lipowczan,[27] Zera,[28] Mły´nski, Zera and Kozłowski [29] as well as Mły´nski and Kozłowski [30] should be mentioned. The hazard criteria of the auditory system by CHABA [31,32] are used in the USA. Referring to the above publications, the different parameters characterizing impulse noise, including time parameters described in Standard No. ISO 10843:1997,[19] are used.
The authors propose a different approach from the classical one, to the assessment of impulse noise in view of assumptions of the index method of noise hazard assessment in the working environment in quarries,[16] as well as taking into account the specificity of blasting works in the quarries. This approach consists of defining new assessment indices related to the energy of impulse. For this purpose, the authors proposed using the A-weighted sound exposure level LAE of a single event (explosion). This level LAE is convenient to use because it includes the noise level and duration of the event. The proposed impulse noise index WHI is determined on the basis of the auxiliary hazard of impulse noise index in the working environment Whi defined by Equation (3):[16] ⎧ ⎪ 0 for L∗EX,8h < 65 dB(A) ⎪ ⎪ ⎪ −9 ⎪ ⎪ ⎨3.19 · 10 · ∗ Whi = 100.1LEX,8h − 1.01 · 10−2 for 65 dB(A) ≤ L∗EX,8h ⎪ ⎪ ⎪ ≤ 85 dB(A) ⎪ ⎪ ⎪ ⎩1 for L∗EX,8h > 85 d B(A) (3) ∗ where LEX,8h = noise exposure level (impulse) referred to an 8-h work day, (dB(A)), defined by Equation (4): t0 ∗ = LAE − 44.6, dB(A) (4) LEX,8h = LAE + 10 log 8h where t0 = reference time, t0 = 1 s, 8 h = 8 × 3600 (s) = 28800 (s), LAE = A-weighted exposure level for a single event (explosion), (dB(A)). The level of exposure to impulsive noise referring to an 8-h work day L∗EX,8h can also be determined with knowledge of the value of the equivalent A-weighted sound pressure level in exposure time (duration of explosion) te , LAeq,te : te , dB(A) (5) L∗EX,8h = LAeq,te + 10 log t0 where te - exposure time, (s), t0 = 8 h = 8 × 3600 (s) = 28800 (s). The hazard of the impulse noise index in the working environment Whi , similarly to the impulse noise index WHC , takes values from 0 to 1. When calculated from Equation (4) (or (5)), the value of L∗EX,8h is less than the assumed value of 65 dB, and the index Whi , according to Equation (3) is 0, which means no impulse noise pollution. The maximum value of the index Whi is equal to 1, which indicates that it has exceeded acceptable levels of L∗EX,8h = 85 dB(A), and the impact of impulse noise from blasting is very harmful. The WHI impulse noise index in the evaluation of the acoustic climate of a quarry is defined by Equation (6): WHI =
Shi(1) , Sc
(6)
International Journal of Occupational Safety and Ergonomics (JOSE) Table 1. The sound power levels of machinery and equipment in the andesite quarry. Sound power level
3. The results of investigations and calculations 3.1. Experimental studies in real conditions The object of the acoustic study was an andesite quarry. The plant uses stationary crushing machines and, occasionally, mobile crushers. The output from blasting is loaded with front loaders and transported from the excavation site to the primary crusher using trucks. Through sievers, crushers and subsequent belt conveyor systems, aggregates of larger fraction are stored directly in the form of embankments on the site, while the aggregate of smaller fraction is transported to the silo loading. From the silos, using trucks, the aggregate is transported to the appropriate embankment on the site. Loading of the aggregate on the transport vehicles (lorries) is carried out using front loaders. In real conditions, (in situ) measurements of noise coming from the machines and equipment involved in the crushing, sifting, transport and loading of aggregate were performed. Machinery and equipment are components of the processing operation of the production line (Figure 1). Figure 2 shows the sound pressure levels in the one-thirdoctave frequency band for one of the machines, which was siever 1. In the acoustic study, measurements of sound pressure level in one-third-octave frequency bands occurring on machines and equipment in the course of their work were made. Then, their sound power levels were determined, in accordance with Standard No. ISO 3746:2010.[17] The values of sound power levels are shown in Table 1. Further experimental studies carried out in the andesite quarry were to measure the level of impulse noise
Machine
Lw(A)
Lw
Lw(C)
Crusher 1 Siever 1 Vibrating feeder Wheel conveyor Conveyor 1 Crusher 2 Sieve 2 Crusher 3 Conveyor 2 Siever 3 Siever 4 Dispenser aggregate for the loading silo
119.0 129.8 107.0 103.3 116.2 129.4 129.7 119.8 105.5 119.5 114.2 99.5
124.8 131.8 117.5 106.2 119.4 132.7 132.0 119.8 110.5 120.1 117.0 103.2
125.3 132.6 118.5 106.5 120.4 133.5 132.4 122.7 112.8 122.1 118.7 104.2
Note: Lw(A) = A-weighted sound power level, dB(A); Lw = sound power level, dB; Lw(C) = C-weighted sound power level, dB(C).
originating from performed blasting. The blasting parameters were as follows: • • • •
the number of holes: 43 (in four rows), the hole length: 17.5 m, the total mass of explosive used: 3111 kg, the weight of spoil: 21,231 Mg.
Measurements were made using a sound level meter, at three measurement points P1–P3, shown in Figure 3, at distances of 86, 155 and 186 m from the point of detonation (Z). Measurement microphones were placed at heights of 1.5 m. Table 2 shows the results of measurements of the background noise and noise levels measured at three points during the explosion. The values of the levels were determined: LAeq = equivalent A-weighted sound pressure level (dB(A)), LAeq(8h) = equivalent A-weighted
110 100
Sound pressure level (dB)
90 80 70 60 50 40
LIN
A
C
20000
12500
Mid-band frequencies of one-third-octave band (Hz)
Figure 2. Sound pressure levels in one-third-octave frequency bands of siever 1. Note: A = A-weighted sound pressure level; C = C-weighted sound pressure level; LIN = sound pressure level.
16000
8000
10000
6300
5000
4000
3150
2500
2000
1600
1250
1000
800
630
500
400
315
250
200
160
125
100
80
63
50
40
31.5
25
30 20
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where S hi(1) = area of the quarry, in which the hazard of impulse noise index in the working environment Whi = 1, (m2 ); S hi(1) can be obtained using simulation studies on the acoustic model of the quarry; S c = total area of the quarry (m2 ).
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Figure 3.
Arrangement of measuring points (P1–P3) during the impulse noise measurement in the andesite quarry.
Table 2. The results of measurements and calculations of noise levels during blasting works. Measurement point Measured situation Background noise levels
Explosion
Measured and calculated parameters (dB)
P1
P2
P3
LAE
54.7
50.3
45.0
LCE LAeq LCeq LAE LCE LAPEAK LCPEAK LAMAX LCMAX LAeq LCeq LAeq(8h) LCeq(8h)
64.5 70.5 67.9 44.4 40 37.2 54.1 60.2 60.1 97.9 81.8 75.6 105.9 98.6 97.0 132.9 109.2 106.3 134.2 113.6 106.7 105.7 85.6 78.8 109.5 101 99.7 88.7 72.6 66.5 96.7 89.5 87.0 53.3 37.2 31.0 61.3 54.0 52.4
Note: LAE = A-weighted exposure level for a single event (explosion); LCE = C-weighted sound exposure level; LAeq = equivalent A-weighted sound pressure level; LCeq = equivalent C-weighted sound pressure level; LAPEAK = peak A-weighted sound pressure level; LCPEAK = peak C-weighted sound pressure level; LAMAX = A-weighted sound pressure level; LCMAX = the maximum C-weighted sound pressure level; LAeq(8h) = equivalent A-weighted sound pressure level, calculated for a reference time interval equal to an 8-h work day; LCeq(8h) = equivalent C-weighted sound pressure level, calculated for the reference time interval equal to an 8-h work day.
sound pressure level (dB(A)), calculated for a reference time interval equal to 8-h work day, LAE = A-weighted sound exposure level (dB(A)), LCE = C-weighted sound exposure level (dB(C)), LCeq = equivalent C-weighted
sound pressure level (dB(C)), LCeq(8h) = equivalent Cweighted sound pressure level (dB(C)), calculated for the reference time interval equal to an 8-h work day, LAPEAK = peak A-weighted sound pressure level (dB(A)), LCPEAK = peak C-weighted sound pressure level (dB(C)), LAMAX = the maximum A-weighted sound pressure level (dB(A)), LCMAX = the maximum C-weighted sound pressure level (dB(C)). Figure 4 shows the sound pressure levels in one-thirdoctave frequency bands for the measurement point (1) located closest to the explosion (distance 86 m). The noise spectrum is dominated by low frequency components.
3.2. Acoustic models of the quarry Based on the determined sound power levels of machinery and equipment working in the andesite quarry, the SoundPlan 7.2 programme [33] calculated the surface distributions of LAeq on the site. Calculations were performed for two cases: • shift 1 (Figure 5) – operating machines 3–12 (shown in Figure 1), • shift 2 (Figure 6) – operating machines 1–2 (shown in Figure 1). The calculation surface was located at a height of 1.5 m above ground level. Based on the results of measurements of sound pressure level, carried out in real conditions, at the three measurement points (P1–P3, Figure 3) the sound power level of the phenomenon of blasting was calculated, assuming that it is an omnidirectional point source with a location shown in Figure 3. The sound power level of the source was calculated using the measured sound pressure level at point P2. The sound power level for blasting equals 148.3 dB, the
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110
Sound pressure level (dB)
100 90 80 70 60 50 40
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Mid-band frequencies of one-third-octave band (Hz)
Figure 4. Sound pressure levels in one-third-octave frequency bands at measurement point P1. Note: A = A-weighted sound pressure level; C = C-weighted sound pressure level; LIN = sound pressure level.
Figure 5. Distribution of equivalent A-weighted sound pressure level LAeq in the andesite quarry for shift 1.
Figure 6. Distribution of equivalent A-weighted sound pressure level LAeq in the andesite quarry for shift 2.
Figure 7. Distribution of equivalent A-weighted sound pressure level LAeq for the phenomenon of blasting in the andesite quarry.
LIN
A
C
20000
16000
12500
10000
6300
8000
5000
4000
3150
2500
2000
1600
1250
800
1000
630
500
400
250
315
200
125
160
80
100
63
50
40
25
31.5
20
30
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K. Kosała and B. St˛epie´n (a)
(b)
Table 3.
Area between isophones. Area (m2 )
Isophone/area 85 80 75 70 65 S0
LAeq (dB)
Designation area between isophones
Shift 1
Shift 2
> 85 80–85 75–80 70–75 65–70 < 65
85 + 80 + 75 + 70 + 65 + < 65
5743.36 6634.27 12292.78 13675.09 15583.99 17717.25
1961.04 4038.44 6788.42 20889.81 17450.49 33140.39
Note: LAeq = equivalent A-weighted sound pressure level; S 0 = the assessed area of the quarry.
A-weighed sound power level is 124.4 dB(A) and the Cweighted sound power level is 141.3 dB(C). The other two measuring points were treated as a reference for the calibration developed in the SoundPlan 7.2 acoustic model of the andesite quarry (Figure 7). Figure 7 shows the distribution of LAeq on the site for the phenomenon of blasting. The calculation surface was located at a height of 1.5 m above ground level.
Percentage of the areas (%)
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Figure 8. Isophones of equivalent A-weighted sound pressure level in the andesite quarry, 65–85 dB(A): (a) shift 1, (b) shift 2. Note: S 0 = the assessed area of the quarry.
50 45 40 35 30 25
shift 1
20
shift 2
15 10 5 0 60+
3.3.
Index analysis of pollution with continuous and impulse noise Using the developed acoustic models of the andesite quarry, Figure 8 shows particular isophones of LAeq , < 65– 85 dB(A) for shifts 1 and 2. The assessed area of the quarry S 0 = 71,646.7 m2 (Equation (1)). Distributions of LAeq , (Figure 8), were the basis for the calculation of the continuous noise indices WHC for two plant operation shifts. The areas between the isophones are shown in Table 3. Figure 9 shows a comparison of rates for divisions of the areas covered by isophones marked as < 65, 65 + , 70 + , 75 + , 80 + , 85 + for two shifts. On the basis of Equation (1), values of continuous noise were determined, which are: for shift 1 WHC = 0.17 and shift 2 WHC = 0.09. WHC values close to 0 indicate good acoustic climate in the andesite quarry, so it is more beneficial in terms of acoustics for employees working on
65+
70+
75+
80+
85+
Designation area between isophones
Figure 9. Percentage distribution of the areas of 65 + , 70 + , 75 + , 80 + , 85 + covered with isophones 65–85 dB in the andesite quarry for shifts 1 and 2.
shift 2. Distribution of level L∗EX,8h on the calculation surface (1.5 m above ground level) is shown in Figure 10. From the distribution of L∗EX,8h it shows that for the investigated phenomena at the site of explosion, the value of this parameter does not exceed the accepted limit value (equal to 85 dB(A), Equation (3)), hence the area of the plant where the hazard of the impulse noise index in the working environment Whi = 1 is equal to 0. Thus, the value of the index impulse noise WHI (Equation (5)), for the investigated phenomenon of blasting is zero, which means no impulse noise exposure in the quarry (total area of the quarry S c = 302,855.3 (m2 )). The value of the index WHI
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Figure 10. Distribution of the level of exposure to impulse noise referring to an 8-h work day L∗EX,8h in the andesite quarry.
is affected by blasting parameters, primarily the resulting lower aggregate weight (21,231 tonnes) compared to the blasting described in [13] (28,930 tonnes of aggregate) and less than twice the amount of explosives used (3111 kg and 7487.5 kg, respectively).
4. Conclusions The study shows that the sound power levels of machines and equipment involved in the two-shift operation process are high (Lw(A) : 100 to 130 dB(A)). Considering the source of the noise, i.e., machines in the various shifts, continuous noise indices are close to 0, meaning no continuous noise pollution (WHC = 0.2 for shift 1; WHC = 0.1 for shift 2). Low values of the noise pollution index were influenced by a large constant value taken from the evaluation of the area of the quarry (amounting to 71,646.7 m2 ). The problem of continuous noise pollution, indicated by higher values of the WHC index, could arise in the case of simultaneous operation of the machines during shifts 1 and 2. Analysis of the phenomenon of explosion, accompanying the blasting works, showed no impulse noise pollution in the andesite quarry, for specific blasting parameters and the relatively small amount of explosives used and the resulting mass of excavated material. The study of noise problems associated with the propagation of noise in the andesite quarry, taking into account continuous and impulse noise, shows that the exploitation of the quarry does not cause excessive noise pollution within it, and thus does not affect the crew located further away from the production line. Sites that could be dangerous in terms of noise are in the immediate proximity of the machine, where operational staff is present. However, such workstations are fitted with noise-proof cabins.
The studies and indices described in the article are elements of the acoustic climate studies in quarries of rock materials (working environment) and the vibroacoustic index of sustainable development.[34] In addition to the two partial indices described, the index of noise hazard at the workstation and the index of sound power of machines were developed. Using the continuous noise index, the effectiveness of anti-noise solutions for machines and equipment operating in the quarry can be assessed, which is proposed by Kosała and Zawieska.[35] Disclosure statement No potential conflict of interest was reported by the authors.
Funding This paper is based on the results of a research task carried out within the scope of the second stage of the National Programme ‘Improvement of safety and working conditions’ partly supported in 2011–2013 – within the scope of state services – by the Ministry of Labour and Social Policy. The Central Institute for Labour Protection – National Research Institute (CIOP-PIB) was the Programme’s main co-ordinator.
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K. Kosała and B. St˛epie´n of occupational safety condition, mine rescue work and public safety with mining and geological activity in 2013 (in comparison with data since 2008)]. Katowice: Wy˙zszy Urzad ˛ Górniczy; 2013. Wy˙zszy Urzad ˛ Górniczy. Choroby zawodowe [Occupational diseases] [cited 2013 April 12]. Available from: http://www.wug.gov.pl/index.php?statystyki/choroby_ zawodowe Wy˙zszy Urzad ˛ Górniczy [State Mining Authority]. Stan bezpiecze´nstwa i higieny pracy w górnictwie w 2009 r. [Occupational safety and health condition in mining industry in 2009]. Katowice: Wy˙zszy Urzad ˛ Górniczy; 2010. Sensogut C, Cinar I. An empirical model for the noise propagation in opencast mines – a case study. Applied Acoustics. 2007;68(9):1026–1035. Afeni TB, Osasan SK. Assessment of noise and ground vibration induced during blasting operations in an open pit mine – a case study on Ewekoro limestone quarry, Nigeria. Mining Science and Technology (China). 2009;19(4):420– 424. doi:10.1016/S1674-5264(09)60078-8 Engel JR, Kosała K. Ryzyko zawodowe zwiazane ˛ z nara˙zeniem na hałas na wybranych stanowiskach pracy w kopalniach surowców mineralnych [Noise-related occupational risk at selected workstations in open pit mines mineral raw materials]. Bezpiecze´nstwo Pracy. 2005;(10): 6–9. Kosała K. Badania i ocena zagro˙ze´n wibroakustycznych na wybranych stanowiskach pracy w odkrywkowej kopalni wapienia [Investigations and estimations of vibroacoustic hazards at chosen workstations in limestone quarry]. In: Materiały XVI Konferencji Wibrotech. Kraków: AGH; 2012. p. 13–14. Pleban D, Piechowicz J, Kosała K. The inversion method in measuring noise emitted by machines in opencast mines of rock material. Int J Occup Saf Ergon. 2013;19(2):321–331. doi:10.1080/10803548.2013.11076989 Engel Z, Piechowicz J, Stryczniewicz L. Podstawy wibroakustyki przemysłowej [The elements of industrial vibroacoustic]. Kraków: AGH; 2003. Pleban D. Acoustic modelling of machines using the inversion method for the purposes of the acoustic assessment of machines. Archives of Acoustics. 2007;32(2): 321–327. Engel JR, Kosała K, Kłaczy´nski M. Hałasy w kopalniach surowców mineralnych emitowane przez roboty strzałowe [Noise in open pit mines of mineral raw materials emitted by blasting works]. In: Materiały XXXIV Zimowej Szkoły Zwalczania Zagro˙ze´n Wibroakustycznych. Gliwice: Polskie Towarzystwo Akustyczne – Oddział Górno´slaski; ˛ 2006. p. 43–52. Engel J, Kosała K. Sources of vibroacoustic hazards in open-pit mines of mineral raw materials. Archives of Acoustics. 2007;32(2): 251–262. Wszołek T, Kłaczy´nski M. Accuracy of assessing the level of impulse sound from distant sources. Int J Occup Saf Ergon. 2007;13(4):433–440. doi:10.1080/10803548.2007. 11105101 Kosała K. Wska´znikowa ocena zagro˙zenia hałasem s´rodowiska pracy w odkrywkowych kopalniach surowców skalnych [Index assessment of noise hazard of work environment in opencast mines of rock material]. In: Materiały 60 Otwartego Seminarium z Akustyki. Rzeszów: Polskie Towarzystwo Akustyczne – Oddział w Rzeszowie; 2013. p. 310–320. International Organization for Standardization (ISO). Acoustics. Determination of sound power levels and sound
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[31] CHABA. NAS-NRC Committee on Hearing, Bioacoustics, and Biomechanics. Hazardous exposure to impulse noise. Washington, DC: National Academy Press; 1992. [32] Jaroszewski A, Jaroszewska A. Hałas impulsowy i wpływ na system słuchowy: (analiza literatury za okres 1978– 1998) [Impulse noise: characterization and effects on the aural system: (analysis of literature for the period 1978– 1998)]. Warszawa: Akademia Muzyczna im. Fryderyka Chopina; 2000.
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ISSN: 1080-3548 (Print) 2376-9130 (Online) Journal homepage: http://www.tandfonline.com/loi/tose20
Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices Krzysztof Kosała & Bartłomiej Stępień To cite this article: Krzysztof Kosała & Bartłomiej Stępień (2016) Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices, International Journal of Occupational Safety and Ergonomics, 22:1, 92-101, DOI: 10.1080/10803548.2015.1106702 To link to this article: http://dx.doi.org/10.1080/10803548.2015.1106702
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Date: 13 March 2016, At: 09:28
International Journal of Occupational Safety and Ergonomics (JOSE), 2016 Vol. 22, No. 1, 92–101, http://dx.doi.org/10.1080/10803548.2015.1106702
Analysis of noise pollution in an andesite quarry with the use of simulation studies and evaluation indices Krzysztof Kosałaa,b∗ and Bartłomiej St˛epie´na
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a AGH
University of Science and Technology, Poland; b Central Institute for Labour Protection – National Research Institute (CIOP-PIB), Poland
This paper presents the verification of two partial indices proposed for the evaluation of continuous and impulse noise pollution in quarries. These indices, together with the sound power of machines index and the noise hazard index at the workstation, are components of the global index of assessment of noise hazard in the working environment of a quarry. This paper shows the results of acoustic tests carried out in an andesite quarry. Noise generated by machines and from performed blasting works was investigated. On the basis of acoustic measurements carried out in real conditions, the sound power levels of machines and the phenomenon of explosion were determined and, based on the results, three-dimensional models of acoustic noise propagation in the quarry were developed. To assess the degree of noise pollution in the area of the quarry, the continuous and impulse noise indices were used. Keywords: noise; machines; quarries; acoustic model; noise evaluation indices
1. Introduction Excess noise in mining, which is one of the noxious agents for health in the workplace, is the cause of occupational diseases and accidents at work. In Poland, there are more than 200 mining companies, employing about 150,000 employees, of whom nearly 20% work in hazardous noise conditions.[1–3] The great importance of this problem is shown in statistics of occupational diseases associated with permanent hearing loss, which indicate that there were 71 such cases in 2010 alone.[1,4] Noise is a noxious agent in surface mining too. In Poland, there are 106 surface mining plants, which employ 15,500 employees. The incidence of occupational disease associated with permanent hearing loss in surface mining in 2004–2009 was 2–7 cases annually.[5] This article concerns noise problems in quarries. Due to the introduction of increasingly modern machinery and equipment, often with increasingly larger size and thus higher power, noise exposure is high. In Poland, in 2009, 93 quarries operated with 2873 people employed.[5] In the technological processes of quarries, the machinery and large-scale equipment used are characterized by high efficiency and also by high emission of acoustic energy. In small- and medium-sized quarries, the noisiest machines are mobile crushers, presenting the greatest risk to workers who operate them. In large plants, however, problems are also connected with stationary crushing machines, located in the production line at high altitudes,
*Corresponding author: Email: [email protected]. © 2016 Central Institute for Labour Protection – National Research Institute (CIOP-PIB)
so the noise is spread in a quarry space at longer distances, thereby threatening all workers in the quarry. An analysis of noise originating from machines and equipment involved in the processing of aggregates showed high values of equivalent A-weighted sound pressure level (LAeq ) at workstations, often in excess of 85 dB(A).[6–9] The study of noise sources on large machines of the crusher-sieve type uses a method of inversion,[10–12] with which it is possible to identify acoustic parameters of substitute sources of sound in the machine or in a team of cooperating machines. The other source of noise in quarries is carried out under the blasting process. Despite the short duration of the detonation of explosives (1–3 s), the phenomenon is accompanied by very high sound levels (peak levels of sound pressure exceed 100 dB).[13–15] This type of noise can be a threat to the health of the quarry workers, local residents and, because of the dominant low-frequency components in the spectrum, a threat to the construction of buildings and objects in the plant and its surrounding area. The main objective of several years of research is to develop innovative methods to assess the noise hazard in the working environment in quarries. The method is based on the single number global index,[16] which is the approximate general measure and the function of four partial indices: the noise hazard index at the workstation, sound power of the machines index, continuous noise index and impulse noise index.
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Verification of the last two indices using the example of a selected andesite quarry is presented in this paper. Determination of the value of these indices requires the development of spatial acoustic models of the quarry, which were used in the context of simulation. Acoustic models are based on the acoustic measurements of the phenomena of blasting and working machines conducted in real conditions. Ultimately, the index method is to be used as a helpful tool in shaping the acoustic climate of a quarry in the context of sustainable development issues.
2.
The investigation methodology of noise pollution in an andesite quarry
2.1. Acoustic tests The methods for determining the sound power levels were based on Standard No. ISO 3746:2010.[17] Depending on the existing conditions, various deviations from the requirements of this standard were made, mostly with the measurement points located above the source of noise and/or points located from the side of other sources of high noise levels being abandoned, or when there was no physical space for the location of the measurement point. The sound pressure level was analysed in the one-thirdoctave bands on the surface surrounding the source, which is either a hemisphere or a cube, depending on the shape of the object and on the conditions in the surrounding space. Measurements of LAeq on the premises of working machinery and equipment are based on the current reference method,[18] whereas the level of exposure to noise from blasting was measured in accordance with Standard No. ISO 10843:1997 [19] at the measurement points P1–P3 (Figure 3). Measurements were made with a SVAN 945 and a SVAN 945A (SVANTEK, Poland) equipped with SV type preamps and ½ inch free-field 40AN microphones from G.R.A.S. The status and schedule of work of each piece of machinery and equipment were recorded and used to develop the acoustic model of the quarry.
2.2. Simulation tests A numerical model for theandesite quarry was developed. All noise sources involved in the manufacturing process carried out by this quarry and located in its area were modelled (Figure 1). In the quarry area, there are stationary noise sources that work on shifts 1 and 2 as well as the impulse noise source (blasting works) occurring periodically. On the basis of elevation map provided by the andesite quarry and the documentation prepared during the visits, a numerical model was developed.
Figure 1. Arrangement of machinery and equipment involved in the process of excavation of andesite. Note: 1 = crusher 1; 2 = siever 1; 3 = vibrating feeder; 4 = wheel conveyor; 5 = conveyor 1; 6 = crusher 2; 7 = siever 2; 8 = crusher 3; 9 = conveyor 2; 10 = siever 3; 11 = siever 4; 12 = dispenser aggregate for the loading silo.
The following assumptions were adopted to build the numerical model: • the model takes into account the digital ground model, • the model takes into account buildings fixed to the ground, additional storeys and woodlots, • all items have a real height. In the final stage of building a model for all types: screening, attenuation and noise sources integration of non acoustic data with acoustic data were carried out. In this way, it was possible to obtain a complete acoustical model of the quarry on the basis of which the A-weighted sound pressure level distributions in its area were calculated. SoundPlan software was used for modelling and mapping. This software allows users to perform calculations based on algorithms recommended in the EU Directive on Environmental Noise 2002/49/EC,[20] taking into account the recommendations contained in Standards No. ISO 13474:2009,[21] ISO 9613-1:1993 [22] and ISO 96132:1996.[23] The developed model was calibrated on the basis of measurement results recorded on September 19–20, 2013. 2.3. Indices of noise pollution in the quarry 2.3.1. Continuous noise index WHC The WHC continuous noise index indicates the status of noise pollution, occurring in a given area of the quarry, originating from plant and equipment involved in the process. Machines used in quarries produce more and more power, including: crushers, sievers, loaders, belt conveyors, stackers, trucks and hammers, and also work in an open space often without adequate noise protection. High
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levels of the sound power of machines (usually in excess of 100 dB(A) (Lw(A) )) are a threat not only locally, in the immediate proximity of the employees operating the machines, but also globally – negatively affecting the climate acoustic environment and posing a threat to other workers. To assess the degree of noise pollution in the quarry, the continuous noise index is proposed and is defined by the equation:[16] 6 κ · S0i , (1) WHC = i=1 S0 where S 0 = the assessed area of the quarry (m2 ), S 0i = the area of the quarry under the curve of equal sound levels of < 65, 65, 70, 75, 80, 85 dB(A) (i = 1, . . . , 6 with curves < 65,65, . . . , 85 dB(A)), (m2 ), κ ratio of hazard from continuous noise, defined by Equation (2): κ=
100.1(LAeq −65) 100.1(85−65)
,
(2)
where LAeq = equivalent A-weighted sound pressure level (dB(A)). Equation (1) is based on the assumption of the permissible value of LAeq , which it is assumed, should not exceed 85 dB(A) during an 8-h work day.[24] To determine the values of WHC it is necessary to establish the distribution of values of LAeq on the assessed area of the quarry. For this purpose, one can use an acoustic model of a quarry that may be developed based on the known sound power levels of sources which are used in plant machines and equipment. The WHC index takes values from 0 to 1. The value WHC = 0 is a good acoustic climate in a given quarry. The impact of continuous noise is then insignificant. The value of WHC = 1 indicates the harmful effects of continuous noise. 2.3.2.
Impulse noise index WHI
In addition to work related to the formation of continuous noise in quarries, blasting is used and is a source of impulse noise, negatively affecting both the external environment [25] and the working environment, which is the area of the quarry. Blasting works are accompanied by high sound pressure levels that may pose a threat to the health of quarry workers. Impulse noise occurring at the workstation in industrial plants is the scope of study and analysis of many researchers. Publications from Coles,[26] Sułkowski and ˙ ˙ Lipowczan,[27] Zera,[28] Mły´nski, Zera and Kozłowski [29] as well as Mły´nski and Kozłowski [30] should be mentioned. The hazard criteria of the auditory system by CHABA [31,32] are used in the USA. Referring to the above publications, the different parameters characterizing impulse noise, including time parameters described in Standard No. ISO 10843:1997,[19] are used.
The authors propose a different approach from the classical one, to the assessment of impulse noise in view of assumptions of the index method of noise hazard assessment in the working environment in quarries,[16] as well as taking into account the specificity of blasting works in the quarries. This approach consists of defining new assessment indices related to the energy of impulse. For this purpose, the authors proposed using the A-weighted sound exposure level LAE of a single event (explosion). This level LAE is convenient to use because it includes the noise level and duration of the event. The proposed impulse noise index WHI is determined on the basis of the auxiliary hazard of impulse noise index in the working environment Whi defined by Equation (3):[16] ⎧ ⎪ 0 for L∗EX,8h < 65 dB(A) ⎪ ⎪ ⎪ −9 ⎪ ⎪ ⎨3.19 · 10 · ∗ Whi = 100.1LEX,8h − 1.01 · 10−2 for 65 dB(A) ≤ L∗EX,8h ⎪ ⎪ ⎪ ≤ 85 dB(A) ⎪ ⎪ ⎪ ⎩1 for L∗EX,8h > 85 d B(A) (3) ∗ where LEX,8h = noise exposure level (impulse) referred to an 8-h work day, (dB(A)), defined by Equation (4): t0 ∗ = LAE − 44.6, dB(A) (4) LEX,8h = LAE + 10 log 8h where t0 = reference time, t0 = 1 s, 8 h = 8 × 3600 (s) = 28800 (s), LAE = A-weighted exposure level for a single event (explosion), (dB(A)). The level of exposure to impulsive noise referring to an 8-h work day L∗EX,8h can also be determined with knowledge of the value of the equivalent A-weighted sound pressure level in exposure time (duration of explosion) te , LAeq,te : te , dB(A) (5) L∗EX,8h = LAeq,te + 10 log t0 where te - exposure time, (s), t0 = 8 h = 8 × 3600 (s) = 28800 (s). The hazard of the impulse noise index in the working environment Whi , similarly to the impulse noise index WHC , takes values from 0 to 1. When calculated from Equation (4) (or (5)), the value of L∗EX,8h is less than the assumed value of 65 dB, and the index Whi , according to Equation (3) is 0, which means no impulse noise pollution. The maximum value of the index Whi is equal to 1, which indicates that it has exceeded acceptable levels of L∗EX,8h = 85 dB(A), and the impact of impulse noise from blasting is very harmful. The WHI impulse noise index in the evaluation of the acoustic climate of a quarry is defined by Equation (6): WHI =
Shi(1) , Sc
(6)
International Journal of Occupational Safety and Ergonomics (JOSE) Table 1. The sound power levels of machinery and equipment in the andesite quarry. Sound power level
3. The results of investigations and calculations 3.1. Experimental studies in real conditions The object of the acoustic study was an andesite quarry. The plant uses stationary crushing machines and, occasionally, mobile crushers. The output from blasting is loaded with front loaders and transported from the excavation site to the primary crusher using trucks. Through sievers, crushers and subsequent belt conveyor systems, aggregates of larger fraction are stored directly in the form of embankments on the site, while the aggregate of smaller fraction is transported to the silo loading. From the silos, using trucks, the aggregate is transported to the appropriate embankment on the site. Loading of the aggregate on the transport vehicles (lorries) is carried out using front loaders. In real conditions, (in situ) measurements of noise coming from the machines and equipment involved in the crushing, sifting, transport and loading of aggregate were performed. Machinery and equipment are components of the processing operation of the production line (Figure 1). Figure 2 shows the sound pressure levels in the one-thirdoctave frequency band for one of the machines, which was siever 1. In the acoustic study, measurements of sound pressure level in one-third-octave frequency bands occurring on machines and equipment in the course of their work were made. Then, their sound power levels were determined, in accordance with Standard No. ISO 3746:2010.[17] The values of sound power levels are shown in Table 1. Further experimental studies carried out in the andesite quarry were to measure the level of impulse noise
Machine
Lw(A)
Lw
Lw(C)
Crusher 1 Siever 1 Vibrating feeder Wheel conveyor Conveyor 1 Crusher 2 Sieve 2 Crusher 3 Conveyor 2 Siever 3 Siever 4 Dispenser aggregate for the loading silo
119.0 129.8 107.0 103.3 116.2 129.4 129.7 119.8 105.5 119.5 114.2 99.5
124.8 131.8 117.5 106.2 119.4 132.7 132.0 119.8 110.5 120.1 117.0 103.2
125.3 132.6 118.5 106.5 120.4 133.5 132.4 122.7 112.8 122.1 118.7 104.2
Note: Lw(A) = A-weighted sound power level, dB(A); Lw = sound power level, dB; Lw(C) = C-weighted sound power level, dB(C).
originating from performed blasting. The blasting parameters were as follows: • • • •
the number of holes: 43 (in four rows), the hole length: 17.5 m, the total mass of explosive used: 3111 kg, the weight of spoil: 21,231 Mg.
Measurements were made using a sound level meter, at three measurement points P1–P3, shown in Figure 3, at distances of 86, 155 and 186 m from the point of detonation (Z). Measurement microphones were placed at heights of 1.5 m. Table 2 shows the results of measurements of the background noise and noise levels measured at three points during the explosion. The values of the levels were determined: LAeq = equivalent A-weighted sound pressure level (dB(A)), LAeq(8h) = equivalent A-weighted
110 100
Sound pressure level (dB)
90 80 70 60 50 40
LIN
A
C
20000
12500
Mid-band frequencies of one-third-octave band (Hz)
Figure 2. Sound pressure levels in one-third-octave frequency bands of siever 1. Note: A = A-weighted sound pressure level; C = C-weighted sound pressure level; LIN = sound pressure level.
16000
8000
10000
6300
5000
4000
3150
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1600
1250
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800
630
500
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315
250
200
160
125
100
80
63
50
40
31.5
25
30 20
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where S hi(1) = area of the quarry, in which the hazard of impulse noise index in the working environment Whi = 1, (m2 ); S hi(1) can be obtained using simulation studies on the acoustic model of the quarry; S c = total area of the quarry (m2 ).
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Figure 3.
Arrangement of measuring points (P1–P3) during the impulse noise measurement in the andesite quarry.
Table 2. The results of measurements and calculations of noise levels during blasting works. Measurement point Measured situation Background noise levels
Explosion
Measured and calculated parameters (dB)
P1
P2
P3
LAE
54.7
50.3
45.0
LCE LAeq LCeq LAE LCE LAPEAK LCPEAK LAMAX LCMAX LAeq LCeq LAeq(8h) LCeq(8h)
64.5 70.5 67.9 44.4 40 37.2 54.1 60.2 60.1 97.9 81.8 75.6 105.9 98.6 97.0 132.9 109.2 106.3 134.2 113.6 106.7 105.7 85.6 78.8 109.5 101 99.7 88.7 72.6 66.5 96.7 89.5 87.0 53.3 37.2 31.0 61.3 54.0 52.4
Note: LAE = A-weighted exposure level for a single event (explosion); LCE = C-weighted sound exposure level; LAeq = equivalent A-weighted sound pressure level; LCeq = equivalent C-weighted sound pressure level; LAPEAK = peak A-weighted sound pressure level; LCPEAK = peak C-weighted sound pressure level; LAMAX = A-weighted sound pressure level; LCMAX = the maximum C-weighted sound pressure level; LAeq(8h) = equivalent A-weighted sound pressure level, calculated for a reference time interval equal to an 8-h work day; LCeq(8h) = equivalent C-weighted sound pressure level, calculated for the reference time interval equal to an 8-h work day.
sound pressure level (dB(A)), calculated for a reference time interval equal to 8-h work day, LAE = A-weighted sound exposure level (dB(A)), LCE = C-weighted sound exposure level (dB(C)), LCeq = equivalent C-weighted
sound pressure level (dB(C)), LCeq(8h) = equivalent Cweighted sound pressure level (dB(C)), calculated for the reference time interval equal to an 8-h work day, LAPEAK = peak A-weighted sound pressure level (dB(A)), LCPEAK = peak C-weighted sound pressure level (dB(C)), LAMAX = the maximum A-weighted sound pressure level (dB(A)), LCMAX = the maximum C-weighted sound pressure level (dB(C)). Figure 4 shows the sound pressure levels in one-thirdoctave frequency bands for the measurement point (1) located closest to the explosion (distance 86 m). The noise spectrum is dominated by low frequency components.
3.2. Acoustic models of the quarry Based on the determined sound power levels of machinery and equipment working in the andesite quarry, the SoundPlan 7.2 programme [33] calculated the surface distributions of LAeq on the site. Calculations were performed for two cases: • shift 1 (Figure 5) – operating machines 3–12 (shown in Figure 1), • shift 2 (Figure 6) – operating machines 1–2 (shown in Figure 1). The calculation surface was located at a height of 1.5 m above ground level. Based on the results of measurements of sound pressure level, carried out in real conditions, at the three measurement points (P1–P3, Figure 3) the sound power level of the phenomenon of blasting was calculated, assuming that it is an omnidirectional point source with a location shown in Figure 3. The sound power level of the source was calculated using the measured sound pressure level at point P2. The sound power level for blasting equals 148.3 dB, the
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Sound pressure level (dB)
100 90 80 70 60 50 40
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Mid-band frequencies of one-third-octave band (Hz)
Figure 4. Sound pressure levels in one-third-octave frequency bands at measurement point P1. Note: A = A-weighted sound pressure level; C = C-weighted sound pressure level; LIN = sound pressure level.
Figure 5. Distribution of equivalent A-weighted sound pressure level LAeq in the andesite quarry for shift 1.
Figure 6. Distribution of equivalent A-weighted sound pressure level LAeq in the andesite quarry for shift 2.
Figure 7. Distribution of equivalent A-weighted sound pressure level LAeq for the phenomenon of blasting in the andesite quarry.
LIN
A
C
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630
500
400
250
315
200
125
160
80
100
63
50
40
25
31.5
20
30
98
K. Kosała and B. St˛epie´n (a)
(b)
Table 3.
Area between isophones. Area (m2 )
Isophone/area 85 80 75 70 65 S0
LAeq (dB)
Designation area between isophones
Shift 1
Shift 2
> 85 80–85 75–80 70–75 65–70 < 65
85 + 80 + 75 + 70 + 65 + < 65
5743.36 6634.27 12292.78 13675.09 15583.99 17717.25
1961.04 4038.44 6788.42 20889.81 17450.49 33140.39
Note: LAeq = equivalent A-weighted sound pressure level; S 0 = the assessed area of the quarry.
A-weighed sound power level is 124.4 dB(A) and the Cweighted sound power level is 141.3 dB(C). The other two measuring points were treated as a reference for the calibration developed in the SoundPlan 7.2 acoustic model of the andesite quarry (Figure 7). Figure 7 shows the distribution of LAeq on the site for the phenomenon of blasting. The calculation surface was located at a height of 1.5 m above ground level.
Percentage of the areas (%)
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Figure 8. Isophones of equivalent A-weighted sound pressure level in the andesite quarry, 65–85 dB(A): (a) shift 1, (b) shift 2. Note: S 0 = the assessed area of the quarry.
50 45 40 35 30 25
shift 1
20
shift 2
15 10 5 0 60+
3.3.
Index analysis of pollution with continuous and impulse noise Using the developed acoustic models of the andesite quarry, Figure 8 shows particular isophones of LAeq , < 65– 85 dB(A) for shifts 1 and 2. The assessed area of the quarry S 0 = 71,646.7 m2 (Equation (1)). Distributions of LAeq , (Figure 8), were the basis for the calculation of the continuous noise indices WHC for two plant operation shifts. The areas between the isophones are shown in Table 3. Figure 9 shows a comparison of rates for divisions of the areas covered by isophones marked as < 65, 65 + , 70 + , 75 + , 80 + , 85 + for two shifts. On the basis of Equation (1), values of continuous noise were determined, which are: for shift 1 WHC = 0.17 and shift 2 WHC = 0.09. WHC values close to 0 indicate good acoustic climate in the andesite quarry, so it is more beneficial in terms of acoustics for employees working on
65+
70+
75+
80+
85+
Designation area between isophones
Figure 9. Percentage distribution of the areas of 65 + , 70 + , 75 + , 80 + , 85 + covered with isophones 65–85 dB in the andesite quarry for shifts 1 and 2.
shift 2. Distribution of level L∗EX,8h on the calculation surface (1.5 m above ground level) is shown in Figure 10. From the distribution of L∗EX,8h it shows that for the investigated phenomena at the site of explosion, the value of this parameter does not exceed the accepted limit value (equal to 85 dB(A), Equation (3)), hence the area of the plant where the hazard of the impulse noise index in the working environment Whi = 1 is equal to 0. Thus, the value of the index impulse noise WHI (Equation (5)), for the investigated phenomenon of blasting is zero, which means no impulse noise exposure in the quarry (total area of the quarry S c = 302,855.3 (m2 )). The value of the index WHI
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International Journal of Occupational Safety and Ergonomics (JOSE)
99
Figure 10. Distribution of the level of exposure to impulse noise referring to an 8-h work day L∗EX,8h in the andesite quarry.
is affected by blasting parameters, primarily the resulting lower aggregate weight (21,231 tonnes) compared to the blasting described in [13] (28,930 tonnes of aggregate) and less than twice the amount of explosives used (3111 kg and 7487.5 kg, respectively).
4. Conclusions The study shows that the sound power levels of machines and equipment involved in the two-shift operation process are high (Lw(A) : 100 to 130 dB(A)). Considering the source of the noise, i.e., machines in the various shifts, continuous noise indices are close to 0, meaning no continuous noise pollution (WHC = 0.2 for shift 1; WHC = 0.1 for shift 2). Low values of the noise pollution index were influenced by a large constant value taken from the evaluation of the area of the quarry (amounting to 71,646.7 m2 ). The problem of continuous noise pollution, indicated by higher values of the WHC index, could arise in the case of simultaneous operation of the machines during shifts 1 and 2. Analysis of the phenomenon of explosion, accompanying the blasting works, showed no impulse noise pollution in the andesite quarry, for specific blasting parameters and the relatively small amount of explosives used and the resulting mass of excavated material. The study of noise problems associated with the propagation of noise in the andesite quarry, taking into account continuous and impulse noise, shows that the exploitation of the quarry does not cause excessive noise pollution within it, and thus does not affect the crew located further away from the production line. Sites that could be dangerous in terms of noise are in the immediate proximity of the machine, where operational staff is present. However, such workstations are fitted with noise-proof cabins.
The studies and indices described in the article are elements of the acoustic climate studies in quarries of rock materials (working environment) and the vibroacoustic index of sustainable development.[34] In addition to the two partial indices described, the index of noise hazard at the workstation and the index of sound power of machines were developed. Using the continuous noise index, the effectiveness of anti-noise solutions for machines and equipment operating in the quarry can be assessed, which is proposed by Kosała and Zawieska.[35] Disclosure statement No potential conflict of interest was reported by the authors.
Funding This paper is based on the results of a research task carried out within the scope of the second stage of the National Programme ‘Improvement of safety and working conditions’ partly supported in 2011–2013 – within the scope of state services – by the Ministry of Labour and Social Policy. The Central Institute for Labour Protection – National Research Institute (CIOP-PIB) was the Programme’s main co-ordinator.
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