EVALUATION AND ANALYSIS OF OCCUPATIONAL NOISE EXPOSURE IN AN AMASSED SAWMILL SITE

Abstract

Modus operandi of wood processing machinery is characterized by high levels of noise which can affect the workers. This study evaluated and analyzed occupational noise exposure of sawmill operators in a sawmill session of a timber market in Ogidi, Anambra state of Nigeria on a recommended noise safety standard criterion by the Nigerian Environmental Standards and Regulation Enforcement Agency (NESREA). The range of the A-weighted equivalent sound pressure level (LAeq) obtained during the sawmill job operations was 85.8-99.7 dBA with a mean value of 95.6 dBA on idling of the machines and 99.3-112.3 dBA with a mean value of 107.1 dBA during the sawing operation. Analysis of the LAeq obtained on a typical noise levels scale showed 100% moderately quiet before and after the job operations and 100% very loud and uncomfortably loud on idling of the machines and sawing operations respectively during the job operation. The independent-samples t-test analyses between the observed noise level at the sawmills during the job operation and the recommended maximum permissible noise level exposure showed statistically significant difference at p< 0.05. The hazardous occupational noise level besetting the sawmill workers established in this study requires safety redress approach for safe work environment.

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JOURNAL OF THE NIGERIAN INSTITUTION OF MECHANICAL ENGINEERS/VOL.9 NO.2 SEPTEMBER 2019
EVALUATION AND ANALYSIS OF OCCUPATIONAL NOISE EXPOSURE
IN AN AMASSED SAWMILL SITE
Adinife P. Azodo1*, Udeme V. Akpan 2, Tochukwu C. Mezue 3, Alexander I. Tyom 4
1, Department of Mechanical Engineering, Federal University of Agriculture, Abeokuta
2 Department of Mechanical Engineering, University of Agriculture, Makurdi, Nigeria
3Department of Electrical and Electronic Engineering, Federal Polytechnic Oko
4Department of Pure and Applied Physics, Federal University Wukari
Abstract
Modus operandi of wood processing machinery is characterized by high levels of noise which
can affect the workers. This study evaluated and analyzed occupational noise exposure of
sawmill operators in a sawmill session of a timber market in Ogidi, Anambra state of Nigeria
on a recommended noise safety standard criterion by the Nigerian Environmental Standards
and Regulation Enforcement Agency (NESREA). The range of the A-weighted equivalent
sound pressure level (LAeq) obtained during the sawmill job operations was 85.8–99.7 dBA
with a mean value of 95.6 dBA on idling of the machines and 99.3 – 112.3 dBA with a mean
value of 107.1 dBA during the sawing operation. Analysis of the LAeq obtained on a typical
noise levels scale showed 100% moderately quiet before and after the job operations and 100%
very loud and uncomfortably loud on idling of the machines and sawing operations respectively
during the job operation. The independent-samples t-test analyses between the observed noise
level at the sawmills during the job operation and the recommended maximum permissible
noise level exposure showed statistically significant difference at p< 0.05. The hazardous
occupational noise level besetting the sawmill workers established in this study requires safety
redress approach for safe work environment.
Keywords: wood, occupational noise, sawmill, exposure, safety
1. INTRODUCTION
Wood as an engineering material has found
its usefulness in its raw state and processed
form in many energy generation utilities
and construction industries. According to
Aruofor (2001), Nigeria is the largest
producer of wood in Africa with an annual
harvest of more than 100 million cubic
meters. This may be attributed to the heavy
dependency of most of the structural and
construction activities in the nation on the
wood resources (Aruofor, 2001). Wood by
nature is adaptable for multiple numbers of
domestic and industrial uses and
applications (Fuwape, 2001). The
maximization of wood potential and the
availability to the end user in commercial
quantity is only possible through
mechanical processes (Babalola et al.,
2018). Mechanical processing through the
use of machines makes wood available in
specific dimensions, sizes, and shapes
(Ohagwua and Ugwuishiwu, 2011). When
felled wood has been processed into beams
and planks, they are called lumber or
timber. The process of reducing wood logs
into desired specifications, grades and
marketable dimensions using sawmill
machinery useful to human societies is
termed sawmilling (Aina, 2006; Babalola et
al., 2018), This, of course, is the major
Journal of NIMechE Vol. 9 No. 2 pp 37-45
Printed in Nigeria
ISSN 2141-2987
Copyright@2019, The Nigerian Institution of Mechanical
Engineers (A Division of the Nigerian Society of Engineers)
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JOURNAL OF THE NIGERIAN INSTITUTION OF MECHANICAL ENGINEERS/VOL.9 NO.2 SEPTEMBER 2019
economic activity of most sawmills
(Babalola et al., 2018).
Every workplace hasone or more prevailing
potential hazard associated with the
involved work process (Azodo and
Adejuyigbe, 2013; Azodoet al., 2018). In
sawmill industries, four types of sawmills
are basically used for the purpose of wood
log conversion to timbers. These include
band, dimensional swivel, rolling table, and
locally manufactured sawmills
(Kambuguet al., 2005 cited in Ssemanda,
2017). The characteristic and modus
operandi of wood processing machinery
coupled with the universal adoption of a
diesel engine for powering most machines
generate high levels of noise which can
influence the workers and the surroundings
(Agyeman-Prempeh, 2014; Owoyemi et
al., 2016). Sawmill machine elements,
cutter heads and circular saws operation
produce noise from structure vibration and
noise radiation of the workpiece or cutting
tool, mechanical resonance frequencies of
the machine frame, cutting tool rotation and
the workplace turbulence, fan dust and chip
removal air carrying systems (Owoyemi et
al., 2016). The hazardous nature of
occupational noise generated by wood
machinery is expressed in terms of the
exposure level and duration (Owoyemi et
al., 2016). Noise intensity and duration of
occupational noise exposure in the sawmill
environment are the volume of lumber and
the work characteristic done by the
machinery on a daily and weekly basis
(Koehncke, 1999; Owoyemi et al., 2016)
characteristically presented factors
affecting wood machinery noise emissions
under four categories as the timber features,
tooling, machine setting and system design.
The distinguishing peculiarity of sawmill
workers noise exposure from other
occupation with high noise potentials is that
most of them are entrepreneurs; as such
regulate their working hours themselves
and are scarcely aware of related
occupational health and safety standards
which predispose them to higher risks of
noise hazards (Odibo et al., 2018).Safety is
a vital and intricate factor to be considered
in the day to day work activities (Ismail et
al., 2010). Occupational health and safety
are interrelated and complementary as it
plays a vital role in the life of workers
(Buksh et al., 2018). Considering that
workers spend significant hours of the day
in their work environment noise
(Otoghileet al., 2018) it is imperative to
objectively and systematically keep under
surveillance the noise levels at the work
environment through reliable noise level
assessment at the workplace (Mika and
Józwik, 2016). Previous research works on
sawmill industries found in literature
considered assessment of noise exposure
intensity level (Ugbebor and Yorkor, 2015;
Adhikari and Sahu, 2016), control strategy
of sawmill noise (Vaishali et al., 2011),
safety approach observed by the sawmill
workers (Mburu and Kiiyukia, 2017;
Thepaksorn et al., 2018), effects of sawmill
noise on workers’ health (Chang and
Chang, 2009; Aremu et al., 2015; Aremu et
al., 2019), effects of safety intervention
practices (Odibo et al., 2018), and
prevalence of cumulative trauma disorders
risk (Adeyemi and Udo, 2016). There is no
known research found in the literature that
considered amassed sawmills in a location
operating almost at the same time.
Therefore, this study evaluated and
analyzed of occupational noise exposure of
sawmill operators in a sawmill sector of a
timber market in Ogidi, the Anambra state
of Nigeria on recommended standard
criteria.
2. MATERIALS AND METHODS
This study was carried out in the sawmill
section of timber market Ogidi, Anambra
state, Nigeria. The timber market is located
on longitude 6.16° and latitude 6.86°. The
regulated daily kick off time of the business
activities in the timber market is from 7:30
am – 5:30 pm Mondays - Saturdays. A total
of 31 sawmill survey sites were used for
this study. For each of the 31 sawmills,
ADINIFE P. AZODO1*, UDEME V. AKPAN 2, TOCHUKWU C. MEZUE 3, ALEXANDER I. TYOM 4
Evaluation and analysis of Occupational Noise Exposure in an Amassed Sawmill site
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JOURNAL OF THE NIGERIAN INSTITUTION OF MECHANICAL ENGINEERS/VOL.9 NO.2 SEPTEMBER 2019
there were two to three operators/workers,
however, only one of the workers’ noise
exposure was assessed. Benetech Sound
Level Meter (SLM) type GM1352 was used
for the measurement of sound levels at-ear
of the operator. The sound level meter was
an internal calibrated sound level with an
accuracy of ±1.5 dB and 31.5 Hz – 8 KHz
frequency response. The resolution setting
was 0.1 dB with a measuring range of 30 –
130 dB. The sound level of each of the
considered sawmill environment was
recorded before the commencement of each
day’s work activity (after 7:30 am) and
after the day’s work (before 5:30 pm).
Since the workers were moving during the
wood sawing operation, a purposefully
designed strap bag which served as the
SLM holder was used at the shoulder of the
workers. The maximum reading of the
SLM for the noise exposure level was
recorded at the idling time of the machines
and during the sawing operations. The SLM
noise exposure assessment was carried out
during the working hours. Each of the 31
sawmill survey sites used for this study
assessed sawmills was surveyed 20 times.
The varying noise levels obtained at each of
the assessed sawmills using the sound level
meter were computed to A-weighted
equivalent sound pressure level (LAeq) for a
single constant noise level value
representation of the total sound energy
being produced over the period of the
assessment.
This was done using the expression:
(
(
1
)
Where
LAeq = A-weighted equivalent sound
pressure level
LAi = A-weighted sound pressure level in
dB
N = total number of measurements
The computed A-weighted equivalent
sound pressure level (LAeq) at each of the
assessed sawmills were analyzed on typical
noise levels scale by Aaberg (2007) to
ascertain the noise intensity of the sawmill
work environments. The categories of the
noise intensity on the typical noise levels
scale is as follows; LAeq ≤ 30 dBA for very
quiet, 30 <LAeq ≤ 50 dBA for quiet, 50
<LAeq ≤ 75 dBA for moderately loud, 75
<LAeq ≤ 100 dBA for very loud and LAeq>
100 dBA for uncomfortably loud noise
levels (Aaberg, 2007; Azodo et al., 2018).
The independent samples t-test analyses
was used to establish if there is a significant
statistical difference between a) the
observed noise level at the sawmills during
the sawing operation and maximum
permissible noise level exposure; b) the
observed noise level at the sawmills at
idling periods of the machines and
maximum permissible noise level
exposure.
The analysis of the obtained data from the
survey was carried out using Statistical
Package for Social Science (SPSS 16.0)
software and Microsoft Excel spreadsheet.
The maximum noise exposure obtained
during the survey were evaluated and
presented in the maximum, minimum,
mean and standard deviation formats.
3. RESULT AND DISCUSSIONS
The descriptive statistical analysis of A-
weighted equivalent sound pressure level of
the 31 sawmills in the selected locations in
the study area are presented on Table 1.
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Table 1. Descriptive statistics of A-weighted equivalent sound pressure level of the sawmills
in the selected locations in the study area
Sawmill
s
Off work hours
Job operation
Morning session
Evening session
Machine Idling
Sawing operation
Min
Ma
x
Mea
n
Min
Ma
x
Mea
n
Min
Max
Mea
n
Min
Max
Mea
n
1
55.
1
62.
0
59.0
52.
4
74.
3
67.6
89.
3
102.
3
96.6
101.
4
107.
2
105.3
2
54.
3
61.
1
57.9
55.
0
72.
9
66.9
85.
0
99.9
96.1
93.0
108.
4
106.3
3
50.
2
59.
3
56.8
54.
0
73.
8
66.7
81.
0
100.
2
95.7
104.
6
110.
0
106.7
4
54.
2
60.
4
57.5
58.
8
76.
2
67.3
83.
0
98.9
95.5
103.
9
120.
0
109.7
5
54.
8
60.
1
58.0
57.
1
72.
0
64.2
86.
0
98.9
94.4
104.
8
119.
0
108.9
6
52.
1
60.
8
58.0
57.
5
74.
4
68.8
82.
0
99.8
95.4
105.
1
109.
0
106.8
7
54.
3
60.
9
57.7
54.
9
72.
7
66.1
81.
0
99.5
96.1
87.0
109.
8
106.9
8
54.
3
60.
0
57.0
52.
2
73.
9
66.0
90.
0
99.0
95.9
99.0
108.
7
106.6
9
53.
0
59.
7
57.1
54.
1
78.
5
68.2
66.
0
99.3
95.5
94.0
109.
1
107.0
10
52.
9
61.
2
57.3
50.
2
73.
0
66.2
91.
0
98.5
96.2
102.
3
108.
9
106.2
11
53.
8
61.
1
57.9
53.
2
70.
6
64.7
89.
0
99.3
95.5
103.
2
133.
0
120.2
12
51.
2
61.
1
57.5
52.
5
71.
6
66.5
86.
1
99.0
95.5
102.
1
122.
0
110.7
13
54.
0
61.
3
57.5
51.
4
73.
0
67.2
81.
0
100.
3
95.8
101.
0
108.
1
106.1
14
54.
4
61.
6
58.0
46.
9
71.
9
65.6
92.
1
99.8
96.3
102.
2
116.
0
106.8
15
47.
0
60.
0
57.4
44.
5
74.
3
66.9
84.
0
98.9
95.5
92.0
110.
0
106.2
16
51.
1
58.
8
56.8
57.
6
74.
5
66.0
82.
0
99.9
95.2
90.0
107.
7
105.0
17
53.
0
59.
9
57.6
56.
8
75.
0
67.1
86.
0
101.
0
95.3
94.0
108.
4
105.1
18
53.
7
69.
9
60.0
56.
2
72.
7
66.0
81.
0
99.8
94.7
101.
7
111.
0
106.1
19
52.
3
61.
7
57.3
58.
9
73.
3
66.0
86.
0
99.5
95.4
101.
2
115.
0
106.8
20
52.
3
61.
5
57.4
56.
4
71.
4
66.2
84.
0
100.
2
95.4
102.
2
111.
0
106.2
21
52.
8
63.
1
58.5
56.
4
71.
2
64.9
80.
0
97.9
94.6
101.
0
112.
0
106.0
22
54.
3
62.
8
58.8
55.
5
73.
7
67.0
91.
8
99.3
95.8
101.
0
107.
5
105.1
ADINIFE P. AZODO1*, UDEME V. AKPAN 2, TOCHUKWU C. MEZUE 3, ALEXANDER I. TYOM 4
Evaluation and analysis of Occupational Noise Exposure in an Amassed Sawmill site
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23
53.
1
60.
7
57.8
53.
8
71.
1
66.1
83.
0
99.5
95.6
91.0
111.
8
106.3
24
53.
0
60.
4
57.6
55.
1
72.
6
64.3
86.
0
102.
0
96.0
94.0
107.
3
105.3
25
54.
7
60.
0
57.6
50.
6
72.
8
67.5
89.
0
99.0
95.2
103.
9
121.
0
110.1
26
53.
5
62.
2
58.3
51.
6
71.
9
67.2
87.
0
98.2
94.2
102.
6
120.
0
109.8
27
53.
9
61.
3
57.5
51.
2
72.
4
66.9
86.
0
99.8
94.8
101.
8
107.
7
105.8
28
55.
3
60.
4
57.8
52.
6
73.
9
65.8
90.
7
100.
1
95.8
102.
7
122.
0
110.5
29
52.
8
67.
8
58.6
54.
4
73.
0
67.6
87.
0
101.
7
96.3
102.
0
104.
9
103.5
30
53.
6
61.
8
58.2
51.
7
73.
8
66.6
80.
0
101.
7
96.1
101.
1
108.
0
103.3
31
53.
6
61.
3
58.0
54.
1
70.
6
65.3
83.
0
99.8
95.9
91.0
105.
9
103.6
The range of the A-weighted equivalent
sound pressure level in the market showed
that 85.8–99.7 dBA with mean value of
95.6 dBA on idling of the machines, while
it was 99.3 – 112.3 dBA with mean value of
107.1 dBA during sawing operation (Table
2). This study buttressed Vaishali et al.
(2011) and Owoyemi et al. (2016)
statement that noise emission of an idling
wood machinery during job operation can
be as high as 95dBA. The noise level
obtained in this study is similar to the
varying noise level operation range of from
80 to 120 dBA by Vaishali et al, (2011) and
Owoyemi et al. (2016).Also the noise
exposure range is similar to the outcome of
Adhikari and Sahu (2016) study which was
92.1 - 116.3 dBA. The mean value of 107.1
dBA obtained in this study is similar but a
little higher with Odibo et al.(2018) study
who obtained 101.08, 102.36 and 105.54
dBA from three different sawmill locations.
The variation in the A-weighted equivalent
sound pressure level obtained in this study
compared to previous studies may be
attributed to the amassed siting of the
sawmills. The LAeq obtained in this study is
higher than the recommended continuous
exposure limit of 85 dBA by NESREA. The
noise exposure level observed in this study
has noise induced occupational injury
potentials on the sawmill workers (Zhao et
al., 1991; Lang et al., 1992;Kryter,
1994).Assessment of the A-weighted
equivalent sound pressure level obtained
from the typical noise levels scale (Aaberg,
2007) to ascertain the noise intensity of the
sawmill work environments showed 100%
moderately quiet during off work hours for
the morning and evening sessions. During
the job operation, on idling of machine the
typical A-weighted equivalent sound
pressure level obtained in the sawmills
were 100% very loud and 100%
uncomfortably loud during the sawing
operations.
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Table 2. Summary of the A-weighted equivalent sound pressure level of the sawmills in the
study area
Activities
Variables
N
Minimum
Maximum
Mean
Working hours
Machine Idling
31
85.8
99.7
95.6
Sawing operation
31
99.3
112.3
107.1
Off work hours
Morning session
31
53.2
61.4
57.8
Evening session
31
53.8
73.1
66.4
Independent-samples t-test analysis between the machine idling noise level and the maximum
permissible noise level
The independent-samples t-test which compared to the statistical significant difference between the
means of the idling machine noise level and the maximum permissible noise level found that the
machine idling noise level during the job operation was of statistical significance. Higher mean values
(mean = 95.56 ± .58, SEM = .58) compared to the maximum permissible noise level (mean = 85.0000
± .0000, SEM = .0000), with t (31) = 102.148, p = .000 (Table 3)considered at the value of "Sig. (2-
tailed)" which was less than 0.05.
Table 3. Independent-samples t-test for noise level between the machine idling noise level and the
maximum permissible noise level
Noise level
characteristics
Group Statistics
Independent Samples Test
N
Mean
Std.
Deviation
Std. Error
Mean
Mean
difference
T
Df
P-value
(Sig. (2-
tailed))
Idling noise level
31
95.5581
.57548
.10336
Maximum
permissible noise
level
31
85.0000
.00000
.00000
10.55806
102.148
60
.000
Independent-samples t-test analysis
between the sawmill machinery sawing
operation noise level and the maximum
permissible noise level,
The result of independent-samples t-test
which was used to test differences in the
means for the two independent groups, the
sawmill machinery sawing operation noise
level and the maximum permissible noise
level if they are significantly different from
each other, found that the sawmill
machinery sawing operation noise level
was of statistical significance with higher
mean values (mean = 107.0613 ± 3.11049,
SEM = .55866) compared to the maximum
permissible noise level (85.0000 ± .0000,
SEM = .0000), with t(31) = 39.490, p = .00
(Table 4). The groups’ means are
significantly different because of the value
of "Sig. (2-tailed)" is less than 0.05. The
findings revealed that the occupational
noise exposure of the sawmill workers at
timber market Ogidi is beyond the
maximum permissible noise exposure level
which unhealthy.
ADINIFE P. AZODO1*, UDEME V. AKPAN 2, TOCHUKWU C. MEZUE 3, ALEXANDER I. TYOM 4
Evaluation and analysis of Occupational Noise Exposure in an Amassed Sawmill site
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Table 4. Independent-samples t-test for noise level between the sawmill machinery sawing
operation noise level and the maximum permissible noise level
Noise level
characteristics
Group Statistics
Independent Samples Test
N
Mean
Std.
Deviation
Std.
Error
Mean
Mean
difference
T
Df
P-value (Sig.
(2-tailed))
Sawing
operation noise
level
31
107.0613
3.11049
.55866
Maximum
permissible
noise level
31
85.0000
.00000
.00000
22.06129
39.490
60
.000
4. CONCLUSIONS
Occupational noise exposure level beyond
the maximum permissible noise level for
health and safety workers poses a big
challenge to the workforce or human
resources of any nation as occupational
health and safety are interrelated and
complementary as such plays an intricate
and vital role in the workers’ life.
Identification of noise exposure level
during jobs operations in an amassed
sawmills and analyzed on the guidelines
and standards for environmental pollution
control in Nigeria recommended for noise
exposure safety by NESREA carried out in
this study showed that workers at the
assessed sawmills were exposed to noise
level beyond the recommended noise
exposure limit 85 dBA during the job
process involved in the sawmills. The
hazardous occupational noise level
besetting the sawmill workers established
in this study requires the machine vibration
reduction through the use of machine
damper between the machine and the
foundation and workers’ personal
protective device
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ADINIFE P. AZODO1*, UDEME V. AKPAN 2, TOCHUKWU C. MEZUE 3, ALEXANDER I. TYOM 4
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