مقایسه تراز فشار صوت دو نوع کمباین مورد استفاده در ایران و بررسی برخی از عوامل موثر بر آن

Background and aims: High levels of noise that most operators of agricultural machinery are exposed to for a long time contribute to cause chronic fatigue and irreversible hearing loss. For this reason, occupational health and safety issues related to such machinary should be considered as a key criterion in the design of agricultural machinery and as a critical factor in the acceptance and sales of these equipment. In this study, some factors affecting the sound pressure level of two combines were evaluated.  Methods: Accordingly, sound pressure level of John Deere 1055 and Sampo 3065 combine harvesters were evaluated at the operator's ear, 7.5 and 20 meters of the device. Measurements were performed using a microphone MP201, preamplifier MA231 and MC3022 data acquisition system. A factorial experiment that arranged as a completely randomized design with four replicates was used and data were analyzed using SPSS software version 17.  Results: The results of this study indicate that different levels of the variable gear ratio, type of operation, engine speed and microphone distance was significant on sound pressure level at 1% level. The results also show that the sound pressure level at the ear position in the combines without cab is greater in comparison to other distances. Sampo and John Deere combine cabs reduce noise level to 5.67 and 9.39 dB, respectively. Conclusion: The results of this research revealed the existence of a cabin in both types of combine harvesters, had a significant impact on the reduction of noise level that the use of cab in John Deere in comparison to Sampo, reduced noise levels to a greater degree. But what is certain is that large numbers of combine harvesters that currently are used in different regions of the country are without the cabin. Regarding the use of these combine harvesters, hearing protection is absolutely essential.