Effects of noise on operatives with machine interaction in manufacturing environments Ilaria Lombardi 1 Department of Industrial Engineering, University of Campania “Vanvitelli” Aversa, 81031, Italy Antonella Bevilacqua 2 Department of Industrial Engineering, University of Parma Parma, 43121, Italy Sonia Capece 3 Department of Industrial Engineering, University of Campania “Vanvitelli” Aversa, 81031, Italy Mario Buono 4 Department of Industrial Engineering, University of Campania “Vanvitelli” Aversa, 81031, Italy

ABSTRACT Human-machine interaction is an ordinary paradigm in the manufacturing industry. This area of business has to ensure high level of safety in order to protect the operatives while performing their tasks. When the safety criteria are not met nor controlled, psychological disease and physical injuries can be developed in the working environments. The effects could lead to short or long-term illnesses such as tinnitus or hearth attacks, in relation to the levels of stress. During the last decades, different methodologies have been developed to analyse and evaluate the parameters linked to the human- machine interaction. These methodologies include the biomechanics overload, the noise and vibration. This paper deals with a case study as representative of the manufacturing sector. The noise and vibration levels of different machines have been extracted by a database of been measured on site by using a class 1 sound level meter. The purpose of the paper is to carry out a data analysis, assuming a long-term projection of the physical and psychological effects that could affect the operatives in case of any criteria has not been met.

1. INTRODUCTION

The ergonomics or Human Factors (HF) in work environments has improved the health and safety of operatives by adapting machines and tools to human capabilities, with respect to their limitations and anatomic configuration. Work systems are built upon the potentialities of tools and machinery along with the usability of the system itself. Focus on user-friendly design of technical systems, has been developed by targeting effectiveness, efficiency and also satisfaction of the users [1]. As a result of

1 ilaria.lombardi@unicampania.it 2 antonella.bevilacqua@unipr.it 3 sonia.capece@unicampania.it 4 mario.buono@unicampania.it

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combination between automation and digitization, nowadays the working conditions are subject to dynamic changes, especially in industrial environments [2]. However, concerns for the frequent occupational injuries and fatalities are still warning [3,4]. On a global scale, statistics say that there are about 2 million deaths per year due to accidents at work or to occupational disease, while in Italy the average is about 900,000 accidents per year, without counting deaths from chronic diseases on workplace. It has been studied that 70-90% of these incidents derive mainly from unsafe human actions and this is the main consideration in place to analyze the human errors. In Italy more than six million of people have hearing problems or disorders, and two million of these are affected by deafness because of have been working in noisy environments. Research and practical experiments show that systems that neglect ergonomics are more likely to create occupational illness, operational errors, and accidents, that can be assigned to individuals or to the entire system [5,6]. New forms of human-computer interaction can place high level of stress on employees with negative consequences for psychological health and well-being [2,7]. Noise is defined by the World Health Organization (WHO) as any unwanted sound [8] and in any workplace has now become one of the most important issues. The continuous mechanization of production leads to multiple noise sources and the percentage of workers exposed to this risk factor increases constantly. To better understand what the impact of noise pollution it is necessary to start from the concept of health as it has been defined by the WHO in 1946, to be “ a state of complete psycho-physical and social well-being and not simply the absence of disease” . An unfavorable acoustic environment can potentially be, therefore, a condition of low quality of life. Background noise can affect the performance in employee's daily activities [8]. Operatives complain when high noise levels are in place in the working environments because considered as a potential factor to lower their overall performance. Noise in the workplace can result from stationary or movable equipment, just to consider the construction tools and the transportation vehicles. The health risks associated with hearing damage are clearly measurable and can be assessed with accuracy. Research studies have shown that A-weighted equivalent sound pressure levels between L eq 85 dB(A) and 88 dB(A) are harmful to human ear. Long-time period of exposure to noise levels fluctuating around L eq 85 and 90 dB(A) or above can be cause of permanent hearing loss. Employers have the obligation to safeguard workers from noise risks, especially when the levels approximate threshold limits. Workers exposed to noise levels above L eq 85 dB(A) must be provided with appropriate personal protective equipment (PPE) [9].

2. METHODOLOGIES

An environmental survey has been carried out by using a Class 1 sound level meter Larson Davis (LXT1) as defined by the standards EN60651, EN60804 and CEI 29-4. The verification of the calibration of the instrument was carried out before and after the measurements. The sound level meter was placed at a direct sight of 100 mm from the ear of the worker. Time period given to each measurement was variable, less than 1 minute, to be sufficient to allow the recording of the noise characteristics. The investigation included measurements at specific workstations identified based on information obtained managers and employees related to work patterns and exposure time. The noise measurements are considered representative of the operational activities experienced by each worker during a typical working shift. Details of the operation times of each machine or tool were taken from staff or determined by observation of the process.

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3. CRITERIA

The assessment has been undertaken in accordance with the requirements of the Control of Noise at Work Regulations 2005 (CoNAWR), which specifies action values and exposure limit values for daily personal noise exposure (or weekly personal noise exposure) and peak sound level. These action levels and limits values are summarized in Table 1.

Table 1: Noise threshold within the CoNAWR based on 8-hours.

Sound Pressure Level (dB)

Risk Level Action Value

Exposure L EP,d Peak Noise L CPeak

Low Lower Exposure Action Value

(unprotected) 80 dB(A) 135 dB(C)

Medium Upper Exposure Action Value

(unprotected) 85 dB(A) 137 dB(C)

High Exposure Limit Value (protected) 87 dB(A) 140 dB(C)

The exposure action values are ambient noise levels in the workplace at the worker’s location and do not take into account the effect of any hearing protection. The exposure limit values, however, do consider the effect of hearing protection. 4. CASE STUDY

A baseline noise survey has been conducted across the site of a manufacturing company producing components for windows and doors. In order to assess the prevailing ambient noise levels, measurements of machinery have been compared with the background noise levels at multiple locations, as reported in Table 2.

Table 2: Measured values assessed against the risk class.

Daily Exposur

Time Exposure

Location

No. Sector/Area Leq, dB(A)

Leq , dB(C)

Lpeak,

dB(C)

e Level,

(Hours)

dB(A)

Bench Cutter

– Plastic consumable

1

94 93 116 0.5 82

Bench Saw –

2

Iron consumable

96 96 118 0.25 81

Jig Saw – Aluminum consumable

3

101 99 122 0.5 88

4 Compressor 91 89 122 0.5 79

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Daily Exposur

Time Exposure

No. Sector/Area Leq, dB(A)

Leq , dB(C)

Lpeak,

Location

dB(C)

e Level,

(Hours)

dB(A)

Bench Cutter

– 50mm Aluminium consumable

5

86 85 115 1 76

Bench Cutter

– 25mm Aluminium consumable

6

72 73 99 1 63

Table 2 shows three range of noise levels, specifically it is indicating that noise levels produced in location No. 4, 5 and 6 are found to be lower than LEAV, meaning that the use of ear defenders by employees is not mandatory, but can be worn for comfort purposes. The noise in location No. 1 and 2 have been found to be between the LEAV and the UEAV. In this case a proper selection of hearing protectors mast be available upon request of the employees, but the employers have the duty to provide information to the employees related to the risks associated with the exposure to noise of L eq 81-82 dB(A). In location No. 3 only, the noise levels were found to be exceeding the exposure limit value (ELV), meaning that the hearing protection must be worn by the operatives at all times. Additionally, the employer must establish and implement the health surveillance program related with technical and/or organizational measures intended to reduce the exposure to noise other than designate the specific areas as Hearing Protection Zone. All the noise levels have not been found in excess of peak LEAV. 4. DISCUSSION

It has been discussed above how noise is cause of damage or serious hearing disease (e.g. hypoacusis, deafness), but there are other side effects produced by the exposure to noise that are not directly related to hearing, such as increase of heart-bits rate, blood pressure, nervous and neurovegetative system disorders (dizziness and migraine). All these factors contribute to increase incidents at workplace. However, sometimes risks of overprotection can cause other types of incidents if not appropriate to detect warning devices and signals like alarm. The recommended PPE for this level of noise exposure are the push-in earbuds having attenuation values for each octave as indicated in Table 3.

Table 3: Specification of Ear Defenders. SNR 25dB. Frequency (Hz) 125 250 500 1000 2000 4000 8000 Mean Deviation (dB) 20 21 22 25 36 40 43 Standard Deviation (dB) 4 5 6 3 4 3 4 APV (dB) 16 15 17 22 32 37 39 The following noise computation has been performed for the noisiest locations by considering the use of the indicated ear plugs, as summarized in Table 4.

Table 4: Perceived Sound Pressure Level after PPE Application

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Location

No. Sector/Area Unprotected

Protected

Level

Level

1 Bench Cutter – Plastic consumable 94 65

2 Bench Saw – Iron consumable 96 72

3 Jig Saw – Aluminum consumable 101 65

5. CONCLUSION

The main source of noise in the workplace are dominated by the machinery and plant units that the operator uses on daily base. To reduce the exposure to as low as reasonably practicable (ALARP) specific acoustic measures shall be in place to avoid that the noise would be causing annoyance and other negative effects for the production performance [10]. The measured results reported in Table 2 indicate the workplace most exposed to noise, based on time of exposure on a daily base. To minimize the impact, the employer has the duty of providing the ear protectors especially to the employees working in areas where the noise levels exceed the UEAV. Additionally, the employer shall find alternative solutions, that can involve the task rotation of the employees, the assignment of more breaks, the maintenance of the noisiest equipment and potentially the substitution of pieces of equipment been deteriorated; in addition, some acoustic measures can be represented by the installation of barriers and/or enclosures applied to the sources that can shield the employees from high levels of noise. If the recommended acoustic measures are not in place, the human factor continues to be one of the reasons of occupational accidents. Therefore, it is important to assess, analyze and calculate the level of risk related to noise based on periodical health surveillance of employees, provide appropriate training sessions on the information of the risks related to high noise levels and to the appropriate use of hearing protectors. REFERENCES

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