In the certification of agro-forestry machines, the acoustic pressure levels and, in some cases, also the acoustic power levels are requested by the 98/37/EC Directive. Objective of these values is to protect the operator from the noise risk; for this reason it is very important that they are exact. The acoustic data may vary depending from the machine type, the machine conditions and by the maintenance program operated: in all the cases we could expect to have same acoustic values, but it is demonstrated that we can have similar machines with different acoustic pressure and power levels measured, especially if they have been used since some time, to demonstrate how is difficult to recorder such information to obtain a good repeatability. The current standards include both survey methodologies which consider the scattering of the measured acoustic value and the introduction of corrective factors to determine the allowed range for the measured data. However, the standards do not substitute neither the measurement environment, nor the used instruments. Moreover, the standard cannot guarantee for the operator behaviour in executing the measures. The problem is: how can the environmental conditions, the used instruments and the operator skilfulness contribute to obtain different results in acoustic measures? Objective of this work has been to analyze the acoustic power measurements over the chainsaws. To carry on the tests, three new chainsaws have been used, all of the same manufacturer and of the same model, 50.9 cc of displacement, and 2.3 kW of power, with a bar of 40 cm length. All the machines have been run in and warmed up before the start of each test and carburettors have been adjusted by a specialized technician of the factory. Four set of measurements have been carried out at the laboratory of the IMAMOTER CNR in Turin, using the same standard but in four different period of time, with different air temperatures and with different measurement chains. In all the cases, the EN ISO 22868 standard has been applied in a precise way. As result, using improved measurement systems and respecting the test methodology as requested by the standards, good repeatable values have been obtained, independently by the environment conditions and by the measurement chain.
The acoustic repeatability data declaration for the chainsaws
CALVO, Angela;
2009-01-01
Abstract
In the certification of agro-forestry machines, the acoustic pressure levels and, in some cases, also the acoustic power levels are requested by the 98/37/EC Directive. Objective of these values is to protect the operator from the noise risk; for this reason it is very important that they are exact. The acoustic data may vary depending from the machine type, the machine conditions and by the maintenance program operated: in all the cases we could expect to have same acoustic values, but it is demonstrated that we can have similar machines with different acoustic pressure and power levels measured, especially if they have been used since some time, to demonstrate how is difficult to recorder such information to obtain a good repeatability. The current standards include both survey methodologies which consider the scattering of the measured acoustic value and the introduction of corrective factors to determine the allowed range for the measured data. However, the standards do not substitute neither the measurement environment, nor the used instruments. Moreover, the standard cannot guarantee for the operator behaviour in executing the measures. The problem is: how can the environmental conditions, the used instruments and the operator skilfulness contribute to obtain different results in acoustic measures? Objective of this work has been to analyze the acoustic power measurements over the chainsaws. To carry on the tests, three new chainsaws have been used, all of the same manufacturer and of the same model, 50.9 cc of displacement, and 2.3 kW of power, with a bar of 40 cm length. All the machines have been run in and warmed up before the start of each test and carburettors have been adjusted by a specialized technician of the factory. Four set of measurements have been carried out at the laboratory of the IMAMOTER CNR in Turin, using the same standard but in four different period of time, with different air temperatures and with different measurement chains. In all the cases, the EN ISO 22868 standard has been applied in a precise way. As result, using improved measurement systems and respecting the test methodology as requested by the standards, good repeatable values have been obtained, independently by the environment conditions and by the measurement chain.
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