Occupational exposure to noise in clerical work and effects in workers’ performance: a preliminary study

Human Engineering Group, School of Engineering at the University of Minho/Campus de Azurém/4800-058 Guimarães, Portugal+351 253 510354 / parezes@dps.uminho.ptSantos, Sara M.Faculdade de Engenharia da Universidade do Porto / 4200-465 Porto -Portugal sara_ms@portugalmail.pt

ABSTRACT

ABSTRACT

The main goal of this preliminary study was to analyse the effects of low noise exposure in the cognitive performance of a specific sample of clerical workers. It was intended to assess the association between noise exposure levels and some cognitive characteristics. This analysis has involved a typical office environment, in which noise exposure levels were below the 80 dB(A), which is the lower action level defined in the Portuguese legislation. The first part of this study has consisted in a literature review, in order to collect all the relevant data from previous studies. The second part has consisted in a field study, which was carried out in a real-world context in order to investigate the association between noise exposure and some aspects of the worker’s cognitive performance, namely the perception threshold, the visual info-processing skills, and the reaction time to a visual stimulus. With this aim, a questionnaire and a cognitive assessment test were applied. Simultaneously, background noise exposure levels were measured. From the obtained results it was possible to verify that even in a low noise exposure, lower than 80dB(A), workers can be affected by noise, which has influenced negatively some cognitive aspects, such as the reaction time and the memory abilities. This work has allowed to highlight the potential role played by the exposure to noise levels below 80 dB(A) in worker’s cognitive performance. Effects on the performance of cognitive tasks are also quite significant and, thus, may be included as an occupational risk factor, in particular when companies are designing noise reduction plans or programs.

Keywords

Keywords

Cognitive performance, noise, clerical work.

INTRODUCTION

INTRODUCTION

High noise exposure levels are recognized to be one of main occupational risks. It has been the aim of several studies and its harmful effects in workers’ hearing are legally recognized. Therefore, action levels and the threshold limit values defined in legislation refer to noise exposure levels that might have a significant impact on workers’ hearing.

Although exist a physical and physiological influence, occupational noise exposure might also represent a significant psychological influence on worker, in particular in what concerns his/her cognitive performance. Actually, in some working contexts the existing noise exposure levels aren’t high enough to cause hearing loss

but can affect workers’ cognitive demands, such as concentration, reaction time and memory abilities, wherefore they must be considered as critical aspects in what concerns to the occupational risk.

After a literature review in this domain, an apparent reduced number of studies in this theme was apparently observed, although in the last years the studies in this area have been increasing [1][2][3][4][5][6][7].

The collected data revealed that noise have a significant impact in socialbehaviour and in other human activities, such as work performance, conversation, rest, leisure, and, if extreme scenarios were considered, it could also cause irreversible psychological damages [8][9][10].

Besides, the present legislation [11][12] recognizes noise exposure as an occupational risk that require the protection of workers’ health and safety taking into account the resulting physical consequences. But the legislation also recognizes that the actual scientific knowledge in this area is not enough to cover all the risks, especially those that are not related with the hearing system. Therefore, other associated effects, including psychological, could be detected.

Analysing these studies and the present legislation it was evident that the effects of low noise exposure in cognitive performance exist [13][14] and therefore these potential effects must be faced as a consequence of an occupational risk factor. Thus, it is essential to know how this noise exposure affects workers and their performance while they execute demanding cognitive tasks. Once detected the sources of this deterioration, it will be possible to suggest and to put into practice improvement actions, as well to assess its effectiveness on the attenuation, or elimination, of the problem in an objective way.

In order to analyse the effects of low noise exposure in the cognitive performance of a specific sample of clerical workers, this study consisted in the application of a cognitive assessment test, while the normal activity of other workers was running, with the simultaneous measure of the background noise exposure levels, to assess the association between noise exposure levels and cognitive performance. Therefore, the aim of this preliminary study was to analyse the effects of low level noise exposure in the cognitive performance of a specific sample of clerical workers.

METHODOLOGY

This preliminary study consisted in a field study, which was carried out in a “real-world” context in order to investigate the association between noise exposure and some aspects of the workers’ cognitive performance, namely the perception threshold, the visual info-processing skills, and the reaction time to a visual stimulus.

With this purpose, a questionnaire and a cognitive assessment test were applied. Simultaneously, background noise exposure levels were measured and registered.

The tests took place three times a day (one in the beginning of the morning, other at the end of lunch hour and, the last one, at the end of the working day) during 5 days. Noise measurements occurred whenever a test was accomplished.

Local description

The study took place in two offices (Office1 and Office 2) of a company, where several tasks are functioning simultaneously. Administrative and budget tasks (performed by two persons) coexist in a single office (Office 1), which has 15m2, and office 2, which has 13,5 m2 and is shared by two individuals that are responsible for technical assistance and commercial function.

Each office is an open space that has no physical barrier between desks. These two offices have similar dimension and they are contiguous. The only separation between them is a door that usually is open to facilitate communication among workers.

In this working context, the existing noise level results from several noise sources, such as the phones ringing, conversations, computer’s keyboard noise, printers, fax machine, ventilation and noise from the repair office that is placed at a distance of 4 meters.

Sample’s characterization

Workers’ sample that participated in this study was composed by 4 individuals (two from Office 1 and other two from Office 2). These volunteers participated in a cognitive assessment test and answered to the questionnaire.

The sample was composed by 25% male and 75% female. Worker’s ages were between 28-35 years old (mean age of 30.8 yrs old). Most workers are married, existing only one single person. Two of them have higher education, one has secondary grade and another has the Portuguese obligatory instruction.

Noise measurements and cognitive assessment test

Noise levels were measured with a sound level meter CEL–573.C1, Version 7.2., Type 1, which has been calibrated at the beginning and at the end of each measurement.

In order to assess some aspects of workers’ cognitive performance it was applied a cognitive assessment test in the computer [15]. This test has allowed to evaluate the perception threshold, the visual info-processing skills, and the reaction time to a visual (alphabetic and spatial) stimulus.

As mentioned previously, the test was performed 3 times a day in order to quantify workers’ performance during all working day.

The test consisted in the presentation of a group of 3, or more, letters or shapes (Figure 2a). Right away, a smaller group of letters or shapes was presented to the individual (Figure 2b).

The answer should be given by pressing, quickly as possible, the key “→” (corresponding to an affirmative answer: YES), if one or more letters or shapes of the second group have appeared in the first group (Figure 2c). If none of the letters or shapes have appeared in the first group, the key “←” (corresponding to a negative answer: NO) should be promptly pressured (Figure 2c).

Three different results were obtained with this test (as the example presented in figure 3):

• 1. General score, that refers to the speed and accuracy of the answer (higher values correspond to better performances);
• 2. Average, that shows the average of the reaction time in milliseconds (lower values correspond to better performances);
• 3. %  Correct,  that  refers  to  the  percentage  of  right  answers  (higher  percentages demonstrates better performances).

Figure 2. Cognitive test screenshots.

(a) (b) (c) Figure 3. Screenshots of the chart with the results obtained at the end of the cognitive test.

Questionnaire development and application

The intention of the developed questionnaire was to analyse workers’ reactions to noise in a work context, as well as to verify their perception of its effects in their global performance. With this purpose, the used questions concerned to:

• personal data: age, gender, civil status, academic level;• noise perturbation/annoyance;• noise sources;• perception to the noise’s effects in performance;• modifications in workplace to increase performance;• time spent in workplace.

All the questionnaires should be answered using a Likert’s type scale with the 4 options, “No/nothing”, “Little”, “Moderate” and “A lot”.

To analyse workers’ perception to the influence of noise’s effects in their performance, the following items were presented:

• Concentration;• Motivation;• Attention;• Immediate decision;• Memory capacity;

• Ability to a selection decision;• Client’s conversation;• Reasoningfaculty;• Other, suggested by the workers.

Another questions concerned with the familiarising to noise were asked, as well as workers’ suggestions to modify their workplace were made, in order to realize if they had perception that possible changes could increase their performance through the reduction of noise exposure levels.

RESULTS AND DISCUSSION

Cognitive Tests Results

The cognitive tests were applied every day during a normal labour week and in the normal work schedule. Table 1 presents the results that were obtained.

Table 1 – Results obtained in the cognitive tests performed during a normal working week.

From the obtained results, it was possible to verify some interesting “trends”, namely in what regards:

- Variable SCORE, it is possible to verify that the score decreased while noise exposure levels increased. This occurred during the day (since morning to the end of the day) as well through the week (since Monday to Friday); in most cases, when a raise of noise exposure levels took place the scores declined.

- Variable AVERAGE, it is possible to see that average was proportional to noise.

This means that when noise exposure levels increased, average also increased. This relationship was observed during the day, as well as during the week.

- Variable % CORRECT, it is not possible to identify any direct relationship between the percentage of correct answers and the noise exposure levels.

Comparing the results obtained in the morning with the ones measured at the end of the afternoon, it was possible to observe that all workers had the following

results:

• Lower scores at the end of the afternoon;• Higher average at the end of the afternoon;• Higher percentage of correct answers at the end of the afternoon.

Noise Exposure levels

From the obtained results it was possible to verify that even in a low noise exposure, i.e, lower than 80dB(A), workers can be affected by noise, which has influenced negatively some cognitive aspects, such as the reaction time and memory abilities. This was verified during the working day, as well as along the week.

In this preliminary study, it could be observed that Wednesday and Thursday were the days of the week which it was registered a higher noise exposure levels (Table 2) and were also the days that workers’ performance tended to be lower.

On the other side, Monday was the day of the week with lower noise exposure levels and, accordingly, the day with better results in what concerns cognitive performance.

Table 2 – Noise exposure levels.

Measurement Day Period Leq [dB (A)]

1

2 Monday

Beginning of morning 65,4 Afternoon 67,7

3 End of afternoon                       68,6

4

5 Tuesday

Beginning of morning 71,9 Afternoon 70,8

6 End of afternoon                       71,3

7

8 Wednesday

Beginning of morning 77,2 Afternoon 78,9

9 End of afternoon                       75,7

10

11 Thursday

Beginning of morning 74,3 Afternoon 74,1

12 End of afternoon 72,4

13

14 Friday

Beginning of morning 74,4 Afternoon 75,5

15 End of afternoon 71,1

Comparing the noise exposure levels in the morning with those obtained at the end of the afternoon it was verified that they are lower at the end of the working day. Nevertheless, the results could indicate that noise has an influence in the worker along the day, what could be reflected in the lower workers’ performance at the end of the day.

Questionnaire results

To complete this study it was applied a questionnaire concerning noise in workplace. Table 3 presents the obtained results.

Table 3 – Questionnaire’s results (no. of answers) with the highest no. in grey (shadow).

Question

Answer

2 of the 4 workers considered that some modifications in their workplace should decrease moderately the existing noise and, subsequently, increase their performance. However, other 2 workers considered that this fact hardly influence their performance.

It is not clear the existence of a relationship between the perceived effects and the demographics characteristics of the considered sample, in terms of age/gender/civil state/ background level, as some studies revelled. However, this may be associated with the fact that the sample is not large enough for this kind of relationship verification. Therefore, in future studies the used sample should be enlarged and more homogenous in order to get more credible and accurate comparisons.

From the obtained results it was also possible to verify that the less considered annoying noise was the noise from the keyboard use, following by the fax, printer’s noise and the conversations on the phone. Noise from the ventilation system was the most annoying sound referred by workers, and also the one that affect them more.

In what concerns workers’ perception of the potential noise effects, client’s conversations and the reasoning faculty were referred as those that are not affected by noise. None of the workers considered that noise have a strong influence in the enumerated cognitive elements. They only considered that noise affects moderately

their immediate decision, following by the effects in their concentration, attention and ability to make a decision.

Finally, workers also referred that the existing noise at their workplace annoy them moderately but they admitted that they get used to its presence while they perform their tasks.

CONCLUSIONS

This preliminary study has allowed to highlight the potential role played by the exposure to noise levels below 80 dB(A) in workers’ cognitive performance.

In the studied context, a workplace with cognitive requirements, the existing noise exposure levels were situated between 65 a 80 dB(A), what classifies the noise as annoying.

Some limitations of this preliminary study should be addressed and, accordingly, this study should be completed and applied in different working contexts, as well as with a larger sample.

However, from the obtained results it was possible to verify that even in a low noise exposure not considered by the present legislation, i.e., lower than 80 dB(A), workers can be affected by noise exposure, which has influenced negatively some cognitive aspects, such as the reaction time and the memory abilities. In fact, the majority of workers considered that the noise level has a certain influence in some cognitive features. This indicates that workers had conscience that their cognitive performance is somehow affected, and some of them have even identified the specific source of their disturbance.

Therefore, effects on the performance of cognitive tasks are quite significant and, thus, may be considered as an occupational risk factor, in particular when companies are designing noise reduction plans or programs.

ACNOWLEDGMENTS

Authors wish to thank to all individuals who, voluntarily, participated in this study, to REDIFOGO administration, who gave permission to the fulfilment of this study in their facilities.

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