No abstract

Recent research on the improvement of the noise climate at the operator station of construction machines during real working conditions showed that loudness and sharpness are the parameters best correlated to the annoyance sensation. In order to verify the efficacy of some noise control solutions in improving the operator comfort conditions, it is necessary to detect the minimum differences in these metrics which are subjectively perceived: the just noticeable differences. The subjective listening tests were performed following the classical Method of Limits on a jury of subjects tested one at a time. The subjects were asked to detect the just noticeable differences for both loudness and sharpness sensations, the step size of the stimulus being 0.3 sone and 0.02 acum, respectively. The test was repeated at three different signal presentation levels. Results show that the just noticeable difference in loudness becomes greater as the overall sound pressure level of the signal increases. On the contrary, the just noticeable difference in sharpness has very small variations with the overall level. Focusing on the highest presentation level, 75% of subjects perceives a different sensation when sounds have a loudness difference of at least 0.8 sone and a sharpness difference of 0.04 acum.

This paper describes the results of a study aimed at developing and validating a prediction model to assess the annoyance conditions at the operator station of compact loaders by using noise signal objective parameters only. For this purpose, binaural measurements were carried out on 41 compact loaders, both in stationary and real working conditions. The 62 binaural noise recordings were objectively analysed in terms of acoustic and psychoacoustic parameters and then divided into 9 groups and used in specific jury tests to obtain the subjective annoyance scores. Finally, multiple regression technique was applied to the first 6 groups of noise stimuli to develop the model while the remaining groups were used to validate it.

Since Roll-Over Protective Structures (ROPS) are mandatory on tractors, the number of fatalities caused in the event of an upset is definitely reduced. Nevertheless, fatal accidents caused by machine loss of stability are still of great concern. In fact, despite ROPS have reduced injury to agricultural operators, tractor stability is still a complex issue due to its high versatility in use, especially considering normal operations in field, when interactions with the environment such as soil morphology and climatic conditions are involved, as well as interactions with operator skills and experience. With the aim of collecting data on different variables influencing the dynamics of tractors in field, a commercial device that allows the continuous monitoring of working conditions and the active configuration of the machines was fitted on standard tractors in normal operation at the experimental farm of the Bologna University. The device consists of accelerometers, gyroscope, GSM/GPRS, GPS for geo-referencing and a transceiver for the automatic recognition of tractor-connected equipment. A microprocessor processes data and provides information, through a dedicated algorithm requiring data on the geometry of the tested tractor, on the level of risk for the operator in terms of probable loss of stability and suggests corrective measures to reduce the potential instability of the tractor.