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INTRODUCTION
Metal processing with CNC machine tools
(lathes, milling machines, grinders and others) al-
ways creates certain risks, despite the use of pro-
tective equipment. The majority of such factors
come with time (operation) and it is impossible
to avoid them. This can be attributed, inter alia,
to changes in the work environment, machine
wear, failures, and non-compliance with health
and safety rules. One of these risks is noise. Noise
is dened as any unwanted, unpleasant or inju-
rious mechanical vibration traveling through an
elastic medium which negatively aects the or-
gan of hearing and other elements of the human
body. Energy in an acoustic eld is determined by
the following quantities: sound power LN, noise
level LI or sound pressure Lp. Noise is frequently
dened as any sound which, in given conditions,
is undesirable, tiring or harmful to human health
[2]. Noise-induced hearing loss is one of the most
common occupational illnesses in Europe and it
is present in about one third of all work-related
diseases [16]. Safety is a wide subject of inter-
est and its proper application allows to obtain a
safe product and safe working environment [6–7,
14–15, 17]. Noise minimisation is exceptionally
important in machinery industry, where constant
operation of machinery and devices entails expo-
sition to high levels of noise. Examples of this
Journal of Ecological Engineering
Received: 2017.10.12
Accepted: 2017.10.30
Published: 2018.01.01
Volume 19, Issue 1, January 2018, pages 83–93
https://doi.org/10.12911/22998993/79447
Monitoring of the Noise Emitted by Machine Tools
in Industrial Conditions
Jerzy Józwik1*, Andrzej Wac-Włodarczyk2, Joanna Michałowska3, Monika Kłoczko4
1 Mechanical Engineering Faculty, Department of Production Engineering, Lublin University of Technology,
Nadbystrzycka 36 Str., 20-618 Lublin, Poland
2 Electrical Engineering and Computer Science Faculty, Institute of Electrical Engineering and
Electrotechnologies, Lublin University of Technology, Nadbystrzycka 38a Str., 20-618 Lublin, Poland
3 The State School of Higher Education, The Institute of Technical Sciences and Aviation, Pocztowa 54 Str.,
22-100 Chełm, Poland
4 Aesculap-Chifa Sp.z o.o. Radzyń Podlaski, Budowlanych 3 Str., 21-300 Radzyń Podlaski, Poland
* Corresponding author’s e-mail: j.jozwik@pollub.pl
ABSTRACT
The paper presents an analysis of noise emitted by selected machine tools in a production hall (under industrial
conditions). Noise monitoring is a fundamental task for maintaining workplaces which are safe and healthy. This
paper presents the noise measurements obtained for several machine tools, performed in accordance with the PN
ISO 230–5:2002 standard. The identication of noise sources and levels was conducted by means of the UNIT 352
measurement system for DMU 50, BGO-CNC/RV/R, FU 251, FW 801, FWC 25/H. Detection of noise sources in
the tested machine tools allows to maintain safety of workers and eective means of noise reduction, which are
highly signicant from the perspective of minimising noise at various workstations. The method of performing
noise measurements at workstations using specic machines is normalised, so that the results of such measure-
ments for dierent machines could be compared. The test results were presented in the form of diagrams and
tables. The results of the tests are concluded by a detailed recommendation for the CNC machine tool operators
to use hearing protection when at work. The results showed that the level of noise at the operator’s workstation
signicantly exceeds the standard at certain machining parameters.
Keywords: noise monitoring, measurement, sound pressure, CNC machine tools
Journal of Ecological Engineering Vol. 19(1), 2018
84
include production halls with CNC machines
[4–5, 8–13]. Evaluation of that kind of noise con-
stitutes the basis for using dierent methods of
noise reduction and personal hearing protection
when operating CNC machines [18–19]. Accord-
ing to data provided by the Central Statistical Of-
ce (GUS), 34% of plants out of 3236 noise emit-
ting objects exceeded the allowable noise level
in years 2012–2015. Nearly 40% of Polish em-
ployees employed under harmful and hazardous
conditions (GUS) work in noise exposure levels
of over 85 dbA (the data collected by the Cen-
tral Statistical Oce are incomplete because they
cover only the companies that employ more than
9 people). Reliable measurement of noise cre-
ated a need to prepare a procedure for measuring
the noise emission at CNC workstations. A com-
prehensive procedure of measuring the acoustic
energy emitted by CNC machines is presented
in the Polish standard PN-ISO 230–5:2002. The
standard contains the information on basic condi-
tions for carrying out tests of emission and sound
power, test methods, necessary measuring equip-
ment and the procedure for analysing the results.
Noise is one of the most tiring factors in working
environments. Its impact on the human organism
is dicult to assess [2–3, 20]. Every person work-
ing under industrial conditions is exposed to the
noise levels that very often exceed the allowable
values. The harmful and tiring eects of noise
depend on its intensity, frequency and changes
in time, long-lasting eects and the contents of
inaudible components, as well as certain charac-
teristics of the operators such as age, mental con-
dition, health and individual sensitivity to sounds.
Prolonged exposure to high levels of noise has
negative eects on a person’s health. High lev-
els of noise have a negative eect on well-being,
and – in extreme cases – may lead to hearing im-
pairment. Hearing protection must be worn if the
level of noise is 85 dB or higher [2, 4, 18–20].
Machine tools for cutting metal are a source of
noise. For example lathes, milling and drilling
machines produce noise up to 104 dB, metal cut-
ting saws – up to 115 dB, and grinders – up to
134 dB. There are a couple of standards that sub-
stantially limit the permissible values of the noise
emitted by machine tools. The permissible noise
levels in work environments (NDN values), es-
tablished for hearing protection, are specied by
the Ordinance of the Minister of Labour and So-
cial Policy. These levels are, respectively: noise
exposure level applicable to an 8-hour working
day (LEX,8h) should not exceed 85 dB and the
corresponding daily exposure should not exceed
3.64·103 Pa2·s; in exceptional cases, when the
noise exposure level varies from one working
day to another, the noise exposure level in rela-
tion to the average weekly working time (LEX,
W) should not exceed 85 dB and the correspond-
ing weekly exposure should not exceed 18.2 ·
103 Pa2 · s; the maximum A weighted sound level
(LAmax) should not exceed 115 dB; the peak C-
weighted sound level (LCpeak) should not ex-
ceed 135 dB. The exposure action values are set
out in the Regulation of the Minister of Economy
and Labour on Occupational Safety and Health
for Works Related with Exposure to Noise or Me-
chanical Vibrations. These values are as follows:
noise exposure level applicable to an 8-hour
working day or weekly noise exposure level – 80
dB; the peak C-weighted sound level – 135 dB.
The above-mentioned normative values apply if
other provisions do not specify the lower expo-
sure action values (e.g. in the workstations occu-
pied by young people – LEX,8 h = 80 dB, and
in the workstations occupied by pregnant women
– LEX,8 h = 65 dB). However, as it turns out,
the noise emission in industrial plants is slightly
decreasing, compared to the previous research
periods. Increasingly, the stringent rules for the
protection of health require to reduce the airborne
noise emissions from industrial plants. This is fa-
cilitated by a change of mentality and approach
to the protection of workers’ health as well as the
introduction of new “low-noise” and more “en-
vironmentally friendly” means of production, i.e
machine tools.
RESEARCH METHODOLOGY
The principal objective of the work was to
assess and analyse the noise emitted by machine
tools in a production hall, underindustrial condi-
tions. The research was carried out in Aesculap-
Chifa Sp.z o.o. in Radzyn Podlaski, a company
that manufactures surgical instruments, such as:
tissue grasping forceps, scrapers, scissors, dental
forceps, etc. The noise in the analysed company
is a result of mechanical vibrations, which are
caused by the loss of machine’s basic properties
as well as increasing wear of particular kinematic
pairs, formation of backlash and improper exploi-
tation, machining conditions as well as inade-
quate assembly of basic and auxiliary equipment.
85
Journal of Ecological Engineering Vol. 19(1), 2018
All these factors contribute to the increased noise
levels generated by machine tools. Numerically
controlled CNC machines and conventional NC
machines were monitored. A group of milling ma-
chines marked with the following trade symbols:
DMU 50, BGO-CNC/RV/R, FU 251, FW 801,
FWC 25/H (Figure 1), were placed in the produc-
tion hall (Figure 2).
The noise monitoring process was carried out
in accordance with the strictly dened rules and
regulations contained in the PN-ISO 230–5:2002
standard ”Test code for machine tools – Part 5:
Determination of the noise emission”. This stan-
dard species the procedure for testing the noise
of stationary machine tools and associated auxil-
iary equipment located in a production hall. Aux-
iliary equipment used in the analysed company
includes: heat exchangers, freezer units, hydrau-
lic power packs, extraction equipment and chip
conveyors. UT352 sound-level meters (30–80 dB,
50–100 dB, 60–110 dB, 80–130 dB) were used
for the laboratory and industrial measurements.
According to technical specications of the de-
vice, it is characterised by a high accuracy of
+/- 1.5dB. The measurement channel structure is
shown in Figure 3. The measurements were made
for dierent spindle speeds n: maximum value
nmax, average value navg and minimum value nmin.
Fig. 1. Test stands: a) milling machine DMU 50, b) Berger BGO-CNC/RV/R, c) FU 251,
d) FV 801, e) FWC 25/H
Fig. 2. Arrangement of machine tools in the production hall
Journal of Ecological Engineering Vol. 19(1), 2018
86
A correction lter A was used to measure the
maximum sound level. This lter represents noise
frequency components in the best possible way.
The lters were also used to adjust the readings
of the meter to various characteristics of the hu-
man ear, i.e. so they could represent the actual
acoustic eects. Equally loud sounds with dier-
ent frequencies are perceived by the human ear as
sounds of varying intensity levels. When it comes
to metal cutting machines, as well as most ma-
chines, it is recommended to make measurements
with a correction lter A.
In order to determine the eective value, the
signal passes through the RMS converter that al-
lows integration:
=√1
∫ 2()
0
(1)
The processed signal can be oriented along
the direction of the indicator, enabling to read the
noise level in dB.
The scope of research includes the measure-
ments of noise emitted by 5 metal cutting ma-
chines with similar kinematics and geometrical
characteristics, equipped with computer numeri-
cal control systems CNC and located in the pro-
duction hall, as shown in Figure 2.
Diagnostic evaluation
The process of diagnostic evaluation was car-
ried out in accordance with the scheme covering:
•preparatory work (determining the amount of
measurement points and their locations, start-
ing the machines, dening machine parame-
ters – idling operation and work tests),
•diagnostic evaluation (measurements and
analysis of research results),
•drawing conclusions (comparison and evalu-
ation of the results as compared to the per-
missible value, permissible noise exposure
levels applicable to an 8-hour working day
(LEX, 8 h < 85 dB).
The noise measurements were conducted in
one plane at 8 measurement points during idling
operation and work tests, as shown in Figure 4.
Experimental tests and their results
Noise level monitoring was performed for ve
milling machines, two of which were numerically
controlled machine tools, and the other three in-
cluded conventional machine tools. The research
area is presented in Figure 2. On the other hand,
Figure 4 shows the location, arrangement and dis-
tance between dierent meters in relation to the
machine tool and the operator marked with X.
The meters were located at a distance of 1 m from
Fig. 4. Location of measuring instruments in re-
lation to the machine tool and the operator, X
– location of the operator, d – measurement dis-
tance of meters in relation to the machine tool,
1, 2, .., 8 – measurer position
Fig. 3. Measurement channel structure
87
Journal of Ecological Engineering Vol. 19(1), 2018
the machine tool and at a height of 1.6 m. Mea-
surement microphones were situated horizontally,
along the direction of a given machine tool. These
rules were applied to each tested machine. The
volume of the research area was determined ac-
cording to the following formula (2):
V = a · b · h (2)
where:
a
– length,
b
– width,
h
– height
V = 40 m · 20 m · 6 m = 4800 m3
Background measurements were carried out
for the purpose of making an accurate calculation.
Their value was L’pA = 55.98 dB. The equivalent
acoustic absorption was determined according to
the following formula (3):
= 0.16 · (
)
(3)
where:
V
– volume of the research area,
T
– reverberation time,
A
– equivalent acoustic absorption.
The equivalent acoustic absorption was 419.7
m2 for the characteristic data contained in the (3)
formula, i.e. v = 4800 m3 and T = 1.83 s
The local environmental correction, at a dis-
tance from a given place to the nearest major
sound source from the tested machine a = 1 m,
was determined from the following formula (4):
(4)
After adding the distance value a = 1, and
the equivalent acoustic absorbance A = 419.7
m
2
to the formula (8), the correction value was
K3 = 0.25 dB.
The local environmental correction K3 (cor-
recting element) is expressed in decibels. It de-
pends on the frequency and location, and takes
into account the impact of the reected sound
on the emission sound pressure level at a spe-
cic location of the tested machine tool, e.g. at
the workstation. The A-weighted frequency cor-
rection is marked by K3A. In order to determine
the A-frequency weighted surface sound pres-
sure levels, one must calculate the average of the
measured A-frequency weighted sound pressure
levels. The following sections of this paper con-
tain corresponding formulas used to calculate the
A-frequency weighted surface sound pressure
level. For this purpose, frequency-weighted en-
vironmental corrections K2 were also determined.
The K2 correction is expressed in decibels. It
takes into account the impact of the reected or
absorbed sound on the surface sound pressure
level. As in the case of the K3 correction, the
A-frequency weighted correction is marked by
K2A (5). The dependence of the correction takes
into consideration the unwanted sound that is re-
ected at the objects and walls surrounding the
tested machine. The value of the environmental
correction depends on the target area S and the
equivalent acoustic absorption A.
2 =10lg[1+4(
)]
(5)
The average of the A-frequency weighted
acoustic pressure levels measured by the mea-
suring instrument are used to calculate the sound
pressure level, taking into account the previously
calculated local environmental correction. The
emission sound pressure level is calculated from
the formula (6). It depends on the size of the local
environmental correction and the average of the
A-frequency weighted acoustic pressure levels
contained in table 8.
LpA = LpA
′− K3A
(6)
The A-frequency weighted surface sound
pressure level is calculated from the formula (7).
In order to determine
LpfA
it is necessary to obtain
the A-frequency weighted average of the meas-
urements calculated for the tested machine tool.
(7)
where:
L' pAi
– the frequency weighted sound pres-
sure level measured during operation of
the machine, in the i-th position of the
microphone,
N
– the number of microphone positions
The weighted sound power level is calculat-
ed from the (8) formula. The value of the sound
power level depends on the size of
LpfA
and target
area.
(8)
Journal of Ecological Engineering Vol. 19(1), 2018
88
The exemplary results of the tested machines’
acoustic evaluation, including the results of the
calculations obtained for the tested machine
tools, are presented in Tables 1 to 6. Table 1 pre-
sents the results of noise level measurements
made using DMU 50. Table 2 presents the results
of measurements and calculations of the acoustic
parameters of Berger BGO-CNC/RV/R. Table 3
presents the acoustic evaluation carried out for
the FU 251 milling machine. Table 4 shows the
results of acoustic tests performed for the FW
801 milling machine. Table 5 presents the results
of acoustic tests performed for the FWC 25/H
milling machine.
Figure 5 shows the course of changes in sound
pressure for the tested machine tools (for the DMU
50 machine (Figure 5a), for the BGO-CNC/RV/R
machine (Figure 5b), for the FU 251 machine
(Figure 5c), for the FV 801 machine (Figure 5d)
and for the FWC 25/H machine (Figure 5e)).
The results of the minimum, maximum and
average value measurements of A-frequency
weighted sound power levels – are presented in
Table 6 and the comparison of the ve machine
tools is presented in the bar chart (Figure 6).
The conclusions were drawn upon the context
of the eciency and safety of the operators and
their surroundings. While performing the com-
parative analysis and drawing conclusions, one
should take into account the noise exposure level
applicable to an 8-hour work day or weekly noise
exposure level and the peak sound level. The con-
ducted research permits a more precise control of
the exposure of workers to noise and enables to
improve the machine operating conditions as well
as minimize the negative impact of noise on the
human organism and environment.
CONCLUSIONS
The expansion of the machine park installed
in the company increases the exposure to noise in
the work environment. The machine park of the
company which was the subject of the noise ex-
posure assessment continues to grow and develop,
while the space in which the machines are located
remains unchanged. The noise in the analysed
production plant is not only the result of a large
group of machines and equipment, but also their
parallel operation. The noise generated by ma-
chines increases as they wear out. The conducted
research clearly shows that none of the tested ma-
chines exceeded the limit values permitted by the
relevant standard (85 dB). Nevertheless, it should
be noted that the noise levels (78–78.9 dB) de-
termined by means of experimental and compu-
tational methods are close to the limit value per-
mitted by the standard. Noise is not only danger-
ous for employees in a purely physical, but also
Table 1. Results of noise level measurements and calculations for DMU 50 machine tool
A-frequency weighted sound power levels. LwA 90.8 W
Emission sound pressure level LpA 73.15 dB
Linear dimensions of the target area
(reference cuboid)
l1 + 2 = 4.5 + 2 = 6.5 m
l2 + 2= 4 + 2 = 6 m
l3 + 1 = 2.5 + 1 = 3.5 m
Target area S 117.6 m2
Measurement distance d 1 m
K2A. K3A 3.3 dB; 0.25 dB
A-frequency weighted background noise 55.9 dB
1 2 3 4 5 6 7 8
A-frequency weighted
sound power levels at each
measurement point
1. 71.5 68.4 68.9 71.2 67.5 66.2 65.5 69.3
2. 67.2 66.1 66.7 71.8 65.4 66.6 64.9 67.0
3. 77.8 64.5 86.1 82.7 64.9 68.7 64.8 67.2
4. 80.6 72.8 83.3 82.5 80.5 76.3 67.0 73.9
5. 78.6 81.3 75.1 74.7 79.4 69.7 77.5 82.1
6. 72.4 77.9 71.5 71.3 79.8 79.1 68.5 81.2
7. 69.8 77.2 88.4 83.5 68.5 71.2 70.3 72.6
8. 81.7 68.2 68.3 70.5 67.5 70.4 79.8 79.8
9. 67.2 86.2 68.1 70.4 79.8 85.1 66.9 78.2
10. 76.9 65.2 87.4 69.8 65.6 66.9 73.6 74.6
A-frequency weighted surface sound pressure levels.
͞
70.1 dB
89
Journal of Ecological Engineering Vol. 19(1), 2018
economical way. For the analysed company, it is
recommended to periodically control the highest
permissible concentration (NDS) and the high-
est permissible intensity (NDN). In addition, it
is recommended to reorganize all workstations
and conduct frequent surveys among employees.
What is more, it is recommended for the crossings
between the machines to be at least 0.75 m wide,
and for each employee to occupy at least 2 m2
of oor space. There should be adequate lighting
and ventilation in the room. All other noise sourc-
es should be eliminated to ensure that the noise
levels are not exceeded. The noise in the analysed
company is also emitted by fans, coolant pumps
Table 2. Results of noise level measurements and calculations for Berger BGO-CNC/RV/R machine tool
A-frequency weighted sound power levels. LwA 85.7 W
Emission sound pressure level LpA 68.35 dB
Linear dimensions of the target area
(reference cuboid)
l1 + 2 = 5 + 2 = 7 m
l2 + 2= 3.5 + 2 = 5.5 m
l3 + 1 = 1.5 + 1 = 2.5 m
Target area S 101 m2
Measurement distance d 1 m
K2A. K3A 2.92 dB. 0.25 dB
A-frequency weighted background noise 55.9 dB
12345678
A-frequency weighted
sound power levels at each
measurement point
1. 74.2 70.9 71.1 67.6 70.5 68.4 69.3 68.9
2. 72.6 70.7 69.3 65.6 69.8 70.5 69.5 68.3
3. 71.8 69.8 69.8 66.1 67.1 66.4 70.3 68.6
4. 70.6 67.9 69.5 65.5 67.3 67.5 69.4 66.2
5. 68.6 66.9 70.0 63.8 67.5 69.5 68.6 66.1
6. 69.0 67.3 74.3 68.4 67.1 66.2 68.6 66.8
7. 72.2 70.5 69.4 65.6 70.1 68.9 69.4 68.7
8. 70.5 69.1 70.3 64.5 68.8 67.9 69.2 67.3
9. 69.3 66.6 69.2 66.9 68.9 66.5 69.6 68.2
10. 68.8 66.4 69.4 63.8 68.6 66.5 69.1 65.5
A-frequency weighted surface sound pressure levels.
͞
65.7 dB
Table 3. Results of noise level measurements and calculations for FU 251 machine tool
A-frequency weighted sound power levels. LwA 90 W
Emission sound pressure level LpA 73.05 dB
Linear dimensions of the target area
(reference cuboid)
l1 + 2 = 2 + 2 = 4 m
l2 + 2= 1.5 + 2 = 3.5 m
l3 + 1 = 1.7 + 1 = 2.7 m
Target area S 54.5 m2
Measurement distance d 1 m
K2A. K3A 1.82 dB. 0.25 dB
A-frequency weighted background noise 55.9 dB
12345678
A-frequency weighted sound power
levels at each measurement point
1. 70.4 70.5 72.2 72.1 74.0 69.6 73.4 74.6
2. 70.5 69.8 73.7 73.1 73.8 69.5 75.3 77.2
3. 70.2 70.2 73.5 74.1 75.2 71.2 75.6 74.4
4. 69.9 70.3 73.5 74.0 75.2 70.0 76.0 77.7
5. 70.6 71.0 73.4 74.2 75.4 71.8 73.1 75.4
6. 71.0 71.0 73.6 73.7 75.2 71.7 76.1 78.3
7. 70.1 70.3 73.0 74.6 74.7 70.8 76.1 78.7
8. 70.5 70.7 72.5 74.9 75.0 70.6 76.7 78.3
9. 69.4 70.2 72.6 73.8 75.4 71.6 76.0 78.9
10. 70.4 71.4 73.4 74.4 75.1 71.2 76.8 78.5
A-frequency weighted surface sound pressure levels.
͞
73.5 dB
Journal of Ecological Engineering Vol. 19(1), 2018
90
Table 4. Results of noise level measurements and calculations for FW 801 machine tool
A-requency weighted sound power levels. LwA 93.7 W
Emission sound pressure level LpA 77.65 dB
Linear dimensions of the target area
(reference cuboid)
l1 + 2 = 2. + 2 = 4.2 m
l2 + 2= 1.6 + 2 = 3.6 m
l3 + 1 = 1.8 + 1 = 2.8 m
Target area S 58.8 m2
Measurement distance d 1 m
K2A. K3A 1.93 dB. 0.25 dB
A-frequency weighted background noise 55.9 dB
12345678
A-frequency weighted sound power
levels at each measurement point
1. 76.4 77.3 80.0 79.1 77.5 77.1 75.8 80.2
2. 77.6 75.8 79.8 79.6 78.8 77.9 79.8 80.6
3. 78.3 77.3 79.2 77.5 77.0 77.6 79.3 78.7
4. 78.0 76.8 79.1 79.3 76.9 76.3 78.0 78.4
5. 77.0 76.4 78.1 79.0 76.9 76.6 79.3 78.9
6. 77.6 76.0 78.7 77.5 77.8 76.2 79.9 77.9
7. 77.9 76.7 78.2 78.1 77.4 76.8 78.7 78.2
8. 78.1 76.1 77.9 78.2 78.9 77.4 79.8 77.6
9. 75.3 77.4 78.3 78.9 78.1 76.8 76.2 77.2
10. 77.3 76.2 78.5 78.2 79.9 77.8 78.0 77.0
A-frequency weighted surface sound pressure levels.
͞
75.97 dB
Table 5. Results of noise level measurements and calculations for FWC 25/H machine tool
A-frequency weighted sound power levels. LwA 89.1 W
Emission sound pressure level LpA 73.25 dB
Linear dimensions of the target area
(reference cuboid)
l1 + 2 = 2. + 2 = 4.0 m
l2 + 2= 1.8 + 2 = 3.8 m
l3 + 1 = 1.6 + 1 = 2.6 m
Target area S 55.8 m2
Measurement distance d 1 m
K2A. K3A 1.85 dB. 0.25 dB
A-frequency weighted background noise 55.9 dB
12345678
A-frequency weighted sound power
levels at each measurement point
1. 69.5 71.3 74.1 76.4 73.2 73.6 73.1 74.5
2. 69.9 71.9 73.9 75.1 74.2 76.1 74.9 73.5
3. 69.8 71.9 74.0 75.8 74.2 76.4 74.8 73.8
4. 69.8 71.9 73.9 75.8 74.1 76.3 74.6 73.3
5. 68.4 70.6 73.8 75.5 74.3 76.0 75.3 74.2
6. 69.1 71.3 74.0 76.4 73.2 75.6 74.6 73.7
7. 69.7 71.5 63.9 75.6 74.0 76.4 75.0 73.9
8. 69.8 71.7 74.1 75.6 74.0 76.2 75.0 74.1
9. 69.1 71.2 74.2 75.8 73.4 75.9 74.9 74.2
10. 68.9 71.1 74.0 76.0 73.6 76.2 74.8 74.8
A-frequency weighted surface sound pressure levels.
͞
71.65 dB
Table 6. Summary of minimum, maximum and average noise levels obtained for selected machine tools
Noise level DMU 50 BGO-CNC/RV/R FU 251 FW 801 FWC 25/H
min [dB] 64.50 63.80 69.40 75.30 63.80
avg [dB] 76.45 69.00 74.15 77.95 70.10
max [dB] 88.40 74.20 78.90 80.6 76.40
91
Journal of Ecological Engineering Vol. 19(1), 2018
Fig. 5. The course of changes in sound pressure for the machine:
a) DMU 50, b) BGO-CNC/RV/R, c) FU 251, d) FV 801, e) FWC 25/H
Fig. 6. Comparison of the noise levels obtained for selected machine tools machine tools
Journal of Ecological Engineering Vol. 19(1), 2018
92
and oil pumps. Additionally, it is recommended to
use hearing protectors. Limiting the noise emis-
sion within the production hall should be a prior-
ity, as it is one of the most eective measures to
reduce the risk of exposure of workers to noise. A
few cases identied within the analysed company
showed that a long-term exposure to high levels of
sound can pose serious risks to humans and their
health. Ultrasounds, as well as infrasounds, have
adverse eects on the human nervous system, or-
gans, tissues and hearing. The harmful and tiring
eects of noise depend on its intensity, frequency,
changes in time, long-lasting eects and the con-
tents of inaudible components, as well as certain
characteristics of the operators such as: age, men-
tal condition, health and individual sensitivity to
sounds. High levels of noise have a negative eect
on well-being, and – in extreme cases – may lead
to hearing impairment. Hearing protection must
be worn if the level of noise equals or exceeds
85 dB (A). While comparing the results of mea-
surements of the emission sound pressure levels
for dierent machine tools, it was found that the
values for individual machines do not exceed the
allowable limit values and, in exceptional cases,
they are signicantly lower (by approx. 1 to 30
dB) in relation to the scope of the conducted tests.
The noise emitted by various machines is most
often associated with rotary or reciprocating mo-
tions. In comparison with the data submitted by
the Central Statistical Oce, almost 40% of em-
ployees (in Poland) work under harmful and haz-
ardous conditions. They are most often exposed
to excessive noise, i.e. the noise exposure levels
of over 85 dBA. These data also indicate that the
employees who work for the companies that man-
ufacture products from metal and wood are most
vulnerable. If the sound test procedure permits
the use of several PN-EN ISO 11200 standards or
if there is no sound test procedure, the choice of
method depends on the required accuracy class,
parameters of the available research environment,
size of the machine, nature of the emitted noise
and accuracy classes for measuring instruments.
Limiting the noise emission within the production
hall should be a priority, as it is one of the most
eective measures to reduce the risk of exposure
to noise. Consequently, one of the most important
duties of the machine manufacturer and the user
is to carry out the assessment of machinery noise
emission and take all the necessary measures to
limit this emission.
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