Excessive noise and risks to the machine operator

The expansion of Brazilian agriculture in recent decades has driven manufacturers of agricultural machinery and implements to incorporate new technologies to increase the operational performance of this equipment. Given this demand, there was a significant increase in the dimensions and also an increase in the power of the tractors. Thus, concern arises regarding the safety and comfort conditions of agricultural machinery operators, professionals who, during their working hours, are often exposed to unhealthy factors that can have serious consequences for their health.

An ergonomic factor that is worrying with the increase in dimensions and increase in power of agricultural machines is the operator's exposure to noise. If the noise is excessive, the operator may experience temporary or permanent hearing loss over time, with intensity and exposure being the intensifying factors for this loss or severity of health problems.

The Regulatory Standard (NR-15), in its annex no. 1, establishes that continuous or intermittent noise must be measured in decibels (dB) and with an instrument that measures the sound pressure level. Readings must be taken close to the worker's ear, so that the noise reaching their hearing aid can be captured.

Noise can be characterized according to its sound frequency and the worker's degree of exposure. In the context of agricultural mechanization, the tractor emits high levels of noise also depending on the operation to be carried out, considering that some activities require greater power and increased engine speed.

The use of hearing protection, used by workers who are exposed to excessive noise, is of fundamental importance when operating agricultural machinery. Unfortunately, this usage practice is still little adopted in agriculture. As the noise that the machine produces during operation is harmful to hearing, the use of this protective equipment can minimize or prevent hearing loss. According to NR-15 standards, for a daily exposure period of eight hours, the maximum noise that the operator can be exposed to is 85dB (A), any noise level higher than this characterizes the activity as unhealthy.

Aiming to assess the exposure of agricultural machinery operators to noise, the group of students from the Agricultural Machinery Accident Investigation Laboratory (Lima) assessed the noise level at the agricultural tractor operating station. For this purpose, a Valtra BM 125I tractor with 125 hp of engine power, with and without a hood, was used, carrying out the plowing and subsoiling operation. The methods used in the assessment were in accordance with Regulatory Standard 15 (NR-15) in its Annex I, which establishes the limit of 85dB as the maximum permissible daily exposure limit for an eight-hour working day.

The experiment was conducted in the experimental area of ​​the Agricultural Machinery Accident Investigation Laboratory, belonging to the Federal University of Ceará, on the Pici Campus. Four completely randomized treatments were carried out, T1 being subsoiling with a hood, T2 plowing with a hood, T3 plowing without a hood and T4 subsoiling without a hood, to evaluate whether or not there is a difference in noise level in the aforementioned work situations. To measure continuous or intermittent noise, the dosimeter - DOS-500 was used to collect the noise dose and then convert it to equivalent noise (Equation), for eight hours of work. The dosimeter was attached to the operator's body, with a microphone close to the ear to capture the noises reaching the hearing aid. The collections were carried out after one hour of work, with four collections being carried out daily. Collection times were at 7am, 13pm, 17pm and 20pm, with three repetitions in each treatment. The collected data were allocated to an Excel spreadsheet where averages of the three replications in each treatment were calculated and then statistical analyzes were carried out in Assistat Version 7.6 beta (2013) to check whether there was a significant difference between the treatments analyzed.

Table 1 shows the results of the analysis of variance in which the data presented were significant at the level of 1% probability (p <.01) and to verify whether there is a significant difference between the means of the four treatments presented in the experiment, the means test (Table 2) and the calculation of the Coefficient of Variation (CV).

Table 1 - Table of analysis of variance values ​​for the four treatments of the experiment

FV	GL	SQ	QM	F
Treatments	3	72.62913	24.20971	99.4950**
Residue	44	10.70634	0.24333
Total	47	84.33547

FV

GL

SQ

QM

F

Treatments

3

72.62913

24.20971

99.4950**

Residue

44

10.70634

0.24333

Total

47

84.33547

** significant at 1% probability level (P < .01)

*significant at the 5% probability level (.01 =

ns not significant (p > = .05)

According to the data in Table 2, there was no significant difference at the 5% probability level using the Tukey test between the treatments subsoiling with hood (T1) and plowing with hood (T2). But plowing without a hood (T3) showed a significant difference when compared to subsoiling without a hood (T4) and both in relation to treatments 1 and 2, respectively. The coefficient of variation (CV) found was 0,56, which demonstrates that there was a very low variation between the data presented and that the results are well adjusted to the statistical analysis presented in the experiment.

Table 2 - Comparison of treatment means and Coefficient of Variation

Treatments	Media
T1 - subsoiling with hood	88.91534 to *
T2 - plowing with hood	88.65617 to *
T3 - plowing without hood	85.80812 c
T4 - subsoiling without hood	87.41381 b
CV% = 0.56

Treatments

Media

T1 - subsoiling with hood

88.91534 to *

T2 - plowing with hood

88.65617 to *

T3 - plowing without hood

85.80812 c

T4 - subsoiling without hood

87.41381 b

CV% = 0.56

*Means followed by the same letter do not differ statistically from each other using the Tukey test, at a 5% probability level.

Once we had the means for each treatment, they were compared with the data provided in Annex I of Regulatory Standard 15 to determine whether the noise level measured in the experiment is within the acceptable limit for an eight-hour working day (Table 3).

Table 3 - Comparison of treatment means with the NR-15 table, annex no. 1

Treatments used	Average of Treatments	Maximum daily exposure permissible (NR 15)
T1 - subsoiling with hood	88.91534	4 hours and 30 minutes
T2 - plowing with hood	88.65617	4 hours and 30 minutes
T3 - plowing without hood	85.80812	7 hours long.
T4 - subsoiling without hood	87.41381	5 hours long.

Treatments

used

Average of

Treatments

Maximum daily exposure

permissible (NR 15)

T1 - subsoiling with hood

88.91534

4 hours and 30 minutes

T2 - plowing with hood

88.65617

4 hours and 30 minutes

T3 - plowing without hood

85.80812

7 hours long.

T4 - subsoiling without hood

87.41381

5 hours long.

From the table in Annex No. 1 of Regulatory Standard 15, it was found that Subsoiling with hood and Plowing with hood operations presented noise averages of 88,91dB and 88,65dB, respectively, and compared to NR-15 it is equivalent to four hours and 30 minutes of work; the Plowing operation without a hood presented an average noise of 85,80dB and compared to the NR-15 it is equivalent to seven hours of work and the Subsoiling operation without a hood presented an average noise of 87,41dB and compared to the NR -15 is equivalent to five hours of work.

The vibration of the assembly probably caused the hood to emit certain levels of noise, increasing the operator's acoustic discomfort. Furthermore, removing the hood facilitated the propagation of noise outside the agricultural tractor's operating station.

Given the data obtained in the experiment and compared with the information provided in Table 3 of Regulatory Standard 15 (NR-15), it was possible to prove that in the treatments 1 Subsoiling with hood and 2 Plowing with hood, respectively, the operator can only be exposed in four hours and 30 minutes without using ear protectors; in treatment 3 Plowing without hood, seven hours; and in treatment 4 Subsoiling without hood, five hours. In view of the results, it is recommended that agricultural machinery operators use individual ear protectors during field operations covered in this work.

BOX 1

Equivalent noise equation:

Leq = log

Where:

Lc - This is the level of criteria used (85 according to the Brazilian standard);

% Dose - is the value in % Dose, provided by the device;

Tc - It is the time constant of eight hours;

T - It is the noise measurement time;

N - It is the default value for each standard;

- For N-15, “16,61" is used.

The full article is in Cultivar Máquinas issue 135. Click here to read it.