NOISE LEVELS EMITTED BY AGRICULTURAL TRACTORS WITH AND WITHOUT IMPLEMENTS ACTIVATION

Níveis de ruído emitidos por tratores agrícolas com e sem acionamento de implementos Os níveis de ruído emitidos pelas máquinas agrícolas podem ser prejudiciais à saúde do trabalhador e, por vezes, negligenciados no meio rural. Este trabalho teve como objetivo mensurar os níveis de ruído emitidos por três tratores agrícolas de diferentes potências acionando dois tipos de implementos para avaliar se havia riscos à saúde dos operadores e trabalhadores de apoio ao redor da operação. Os dados de ruído foram coletados por decibelímetro em dez pontos de cada lado da máquina (frente, trás, esquerda e direita) para um total de 40 pontos ao redor de cada trator. Três tratores diferentes foram avaliados em diferentes cenários: sem implemento, acoplando e acionando uma esparramadora de corretivo e acoplando e acionando uma enxada giratória. O trator foi estacionado no centro da mistura com uma rotação do motor que garantiu 540 rotações por minuto (RPM). para a tomada de potência (TDP) durante toda a coleta de dados. Os dados foram analisados ​​por meio de gráficos, regressão linear e análise de agrupamento hierárquico. Os resultados indicaram que os níveis de pressão sonora em todas as situações estudadas ultrapassam os limites da norma regulamentadora (NR) 15, tornando os protetores auditivos indispensáveis ​​durante a jornada de trabalho. Palavras-chave: ergonomia; conforto acústico; mecanização agrícola; nível de pressão sonora. ABSTRACT: The noise levels emitted by agricultural machines can be harmful to the worker's health, and it is sometimes neglected in rural areas. This work aimed to measure the noise level emitted by three agricultural tractors of different power activating two types of implements to assess whether there were risks to operators' health and the supporter workers around the tractor. The noise level data were collected using a decibel meter in ten points on each machine side (forward, rear, left, and right) for a total of 40 points around each tractor. Three different tractors were evaluated in different scenarios: without any implement, coupling and activating a spreader, and coupling and activating a rotary hoe. The tractor was parked at the centre of the mash with an engine speed that ensured 540 rotation per minute (RPM). to the power take-off (PTO) during the entire data collection. The data were analyzed by charts, linear regression, and hierarchical clustering analysis. The results indicated that the sound pressure levels in all of the studied situation exceed the standard's limits regulatory standard 15, making hearing protectors essential during the working day. Keywords: ergonomics; acoustic comfort; agricultural mechanization; sound pressure level.

Vibration and Noise Exposure during Pre-Commercial Thinning Operations: What Are the Ergonomic Benefits of the Latest Generation Professional-Grade Battery-Powered Chainsaws?

In order to compare the vibration and noise exposure of STIHL’s battery-powered MSA 220 C and the combustion driven MS 201 C, a professional operator was monitored during a pre-commercial thinning operation in a twenty-year-old hardwood stand. The vibration levels were measured with a tri-axial accelerometer on the front and rear handle of both the chainsaws, and assigned to five different work elements using a video documentation. Additionally, noise levels were recorded in one-minute intervals, with a dosemeter worn by the operator. The results show that battery-powered chainsaws, when compared to combustion-driven chainsaws, can reduce the daily vibration exposure by more than 45% and the noise dose by about 78.4%, during pre-commercial thinning tasks. Replacing combustion-driven chainsaws with battery-powered ones is therefore generally recommended, to reduce occupational health risks for operators, in this respect. However, the daily vibration exposure of about 2.42 m/s2, caused by the battery-powered chainsaw on the front handle, is still very close to the daily exposure action value set by the EU directives for health and safety requirements. The daily noise exposure of 89.18 dB(A) even exceeds the upper exposure action value. Consequently, a further reduction in the vibration exposure during work is desirable. With respect to noise exposure, additional measures must be implemented for conformity with the current safety standards, making the use of hearing protectors mandatory for electric chainsaws, too.

A comparison of standardized methods for sound attenuation test of hearing protectors

In order to prevent hearing impairment due to occupational noise, it is essential to wear hearing protectors such as earplugs and earmuffs, especially in an extremely noisy environment. The method of measuring their sound attenuation is defined by international standards such as ISO and IEC, and standards such as ANSI, BS, AS/NZS, JIS et.. Although most standards recommend subjective methods where the thresholds of hearing shall be measured once with open ears and once with the hearing protector in place for each subject, measurement and evaluation methods are not unified internationally. In Japan, in April 2020, the old product standard was abolished in consideration of international consistency, and a new method standard was established with the ISO standard as the corresponding international standard for the first time in about 40 years. In this study, we compared the measurement methods and evaluation methods according to the standards for sound attenuation tests of hearing protectors.

Human Temporomandibular Joint Motion: A Synthesis Approach for Designing a Six-Bar Kinematic Simulator

The human earcanal can accommodate several types of in-ear devices including hearing aids, earphones, hearing protectors and earplugs. This canal-type home has a neighbor called the Temporomandibular Joint (TMJ) whose movements slightly deform the shape of the earcanal. While these cyclic deformations can influence the positioning, comfort and functioning of ear-fitted devices, they can also provide a significant amount of energy to harvest. Given their importance, the TMJ movements and earcanal deformations have been well studied. However, their mutual actions are still not fully understood. This paper presents the development of a six-bar kinematic TMJ simulator capable of replicating the complicated motion of the jaw. The development relies on a two-phase mechanism design algorithm to numerically optimize and analytically synthesize linkage mechanisms for which the classical optimization approaches cannot return a converged solution. The proposed algorithm enables the design of a kinematic simulator to generate the TMJ path with an average error as low as 1.65 % while respecting all the hinge-axis parameters of the jaw. This algorithm can be subsequently used to solve nonlinear complex linkage synthesis problems and ultimately, the developed kinematic simulator can be used to further investigate TMJ-earcanal interactions.