جستجوی مقالات مرتبط با کلیدواژه « تراز فشار صدا » در نشریات گروه « مکانیزاسیون کشاورزی »

Hearing loss due to harmful sound is one of the most important occupational illnesses. Agricultural mechanization with the use of a variety of machinery causes problems in occupational safety and health for those working in this field. In this study, some of the factors affecting the noise generated by a garden tractor (H.938 Model) were evaluated and predicted. The tests were performed according to international standards of sound such as ISO 5131 and ISO 7216 at different engine speeds, gear positions, road type and microphone distance. The total number of treatment combinations for extracting sound signals released by the garden tractor reached 216 with 72 treatments and three repetitions. The obtained data were analyzed in the form of a factorial test based on a completely random plan. Besides, Artificial Neural Network and ANFIS model was created to predict the sound level in the aforementioned tractor with 216 patterns for training and assessment. The results of the research showed that the effect of the main factors on the level of sound emitted by the garden tractor were significant at probability level of 1%. The results of frequency analysis showed that noise pressure level decreases according to increase in frequency and the sound intensity that reaches the driver's ear is equal to 77.93 dB at the frequency of 4000 Hz. The results of Artificial Neural Network and ANFIS model for forecasting the Sound pressure level of the garden tractor with the highest coefficient of determination (R2) for this research were 99.73 and 99.91, respectively.

There are several sources of noise in an industrial and agriculture environment. Machines with rotating or reciprocating engines are sound-producing sources. Also, the audio signal can be analyzed to discover how well a machine operates. Diesel engines complex noise SPL and sound frequency content both strongly depend on fuel combustion, which produces the so-called combustion noise. Actually, the unpleasant sound signature of diesel engines is due to the harsh and irregular self-ignition of the fuel. Therefore, being able to extract combustion noise from the overall noise would be of prime interest. This would allow engineers to relate the sound quality back to the combustion parameters. The residual noise produced by various sources, is referred to as mechanical noise. Since diesel engine noise radiation is associated with the operators’ and pedestrians’ discomfort, more and more attention to being paid to it. The main sources of noise generation in a diesel engine are exhaust system, mechanical processes such as valve train and combustion that prevail over the other two. In the present work, experimental tests were conducted on a single cylinder diesel engine in order to investigate the combustion noise radiation during stationary state for various diesel and biodiesel fuel blends.

The engine used in the current study is an ASHTAD DF120-RA70 that is a single cylinder 4 stroke water cooled diesel engine and its nominal power is 7.5 hp at 2200 rpm. The experiment has been done at three positions (Left ear of operator, 1.5 and 7.5 meter away from exhaust) based on ISO-5131 and SAE-J1174 standards. For engine speed measurement the detector Lurton 2364 was utilized with a measurement accuracy of 0.001 rpm. To obtain the highest accuracy, contact mode of detector was used. The engine noise was measured by HT157 sound level meter and was digitalized and saved with Sound View software. HT157 uses alow impedance, capacitor microphone with a unidirectional pattern whose size, sensitivity and frequency range are 1/2", 50 mV Pa-1 and 10 Hz to 20 kHz with a flat extrusion, respectively. Choosing the combination of fuel was carried out according to experiments that have been done before determining engine operation parameters.

Fuel type has a direct effect on the quality of the IC engine's combustion phenomenon. One of the most important quality parameters that can be fluctuated by fuel type is engine noise. The fuel type has a direct effect on internal fuel ignition engines and affects the quality of fuel ignition. One of the effects of ignition quality is the sound of the engine that is very important in terms of both the health and evaluation of engine performance. Two-wheel tractors are of the most important tools used in agriculture. In addition to agricultural work, they have applications in rural areas as power generators. No research has been carried out so far in Iran on the sound of two-wheel tractors fuelled with diesel and biodiesel fuels. Therefore, the sound of the ignition of biodiesel and diesel mixtures in four stroke, single cylinder, two wheel diesel tractors manufactured by Ashtad Company was studied. The purpose of this study is to analyze the noise parameters of a diesel engine using B0, B5, B10, B15, B20, B25 and B30 biodiesel–diesel blends. Biodiesel was produced from waste oil and blended with net diesel fuel to evaluate the Power tiller's engine noise parameters. This study was carried out at a stationary position and at three positions such as driver's left ear position (DLEP), 1.5 meter (1.5 MAFE) and 7.5 meters (7.5 MAFE) away from the exhaust at 6 engine speeds (1200, 1400, 1600, 1800, 2000 & 2200 rpm). Statistical analysis and frequency analysis were used to analyze sound of the engine. The results showed that the sound pressure levels of the engine for B10 fuel have the least amount of noise level of the sound pressure. However, this fuel has no significant difference at 1% level with B00, B05 and B15 fuel. At the A weight level, that matches the structure of the human ear, and there is no difference between the sound pressure levels of ignition. Sound pressure level increased with increasing engine speed and the difference is significant at the 1% level. With increasing speed engine, noise levels increased up to 7.8 dB. Average sound pressure level was 83.76 dB at the driver's ear position (79.3 dBA), at 1.5 meters away from exhaust it was 85 dB (80.9 dBA) and at 7.5 meters away from exhaust it was 79.5 dB (72.4 dBA). The results proved that the lowest and highest sound pressure levels (SPL) of power tiller take place at B10, and B30, respectively. The SPL increased by 7.8 dB for increasing engine speed from 1200 to 2200 rpm. The test results showed that the average SPL at DLEP was 4.3 dB higher than 7.5 MAFE position.

B10 has minimum sound pressure level (SPL), but its difference with B00 (DIESEL FUEL), B05 and B15 is not significant in 1% error level. Considering the NOISH standard, the operator can work with a machine for 8 hours. In DLPE position, the most overcome frequency is 315 Hz for all blends that resulted from exhaustion and combustion. B10 has a minimum SPL at this peak point significantly lower than other blends. For the used engine in this experiment, by optimizing muffler design it is possible to reduce SPL of engine in this frequency peak point.

Workplace factors such as sound must have the minimum impact on the operators of combine harvester، so that they can guide and control many functions of the combine. In this study، some factors affecting the noise generated by two combine harvesters John Deere 1055 and Sampo 3065 were evaluated. Research factors were engine speed، gear ratios، type of operation and microphone distance. The results of this study indicated that sound pressure level decreased with increasing center frequencies. The sound pressure level of John Deere and Sampo combine at center frequency of 4000 Hz were 87. 96 and 84. 73 db، respectively. The results showed also that the maximum sound pressure of John Deere and Sampo combines were116db at frequency of 250 Hz and 111. 1db at frequency of 40 Hz، respectively.

Equipment and machinery used in Agricultural field produce sounds with wide spectrum. Therefore operators and other workers exposed to these sounds. In this study, effects of some factors on emitted noise of a Honda GXV 160 power lawn mower in three different distances were studied. The experiments were carried out based on a factorial statistical design in the form of randomized complete block design with four replications. Sound level measuring device and their establishment and set up were selected in which according to acquired data, the emitted noise level of power lawn mower could be calculated. The results showed that, there exists a significant relationship at 99% levels of probability between the levels of blade rotational speed and emitted noise. But no significant relationship was observed between the levels of collecting basket, operation type and emitted noise. Also results reveal the great sound level at operator’s ear position in comparison with other positions. According to permitted exposure noise level, the received noise level of operator was hazardous and using of hearing protection devices is mandatory. But the received noise level of other workers in field was not hazardous.