Measurement of the emission sound pressure level - a study of deviations using the existing standards and proposal of improvements

摘要

The declaration of noise emission is based on the two quantities sound power level L{sub}w and emission sound pressure level L{sub}p. Although it is only campulsory to declare the sound power level of a machine according to the machine directive if the emission sound pressure level exceeds 85 dB(A), both values are necessary if the sound pressure level at workplaces shall be determined in the planning phase of a plant The determination of the Emission-Sound-Pressure-Level is described in the standards ISO 11201-11205. The main content of these standards is a description of a method how to correct the sound pressure level measured at the defined position from the influence caused by the environment using an environmental correction K{sub}3. With this research project the uncertainties have been examined that result from the application of these standards. It is shown that the "true value" of the environmental correction K{sub}3 depends mainly on the difference L{sub}(w-p) of Sound Power Level and Emission Sound Pressure Level as on the equivalent absorption area A of the room. This difference can be determined for given machine configurations using computer based simulation techniques. The main principles implemented with such a computer program are described. The comparison of the "true value" with that determined with the standardized procedure for a given machine configuration shows the deviation resulting from an application of the standard. On the basis of this knowledge modifications and improvements can be proposed. The result of this study is that the applicability of the standards ISO 11201, -202 and -204 could be improved with some modifications. For each of these standards such recommended improvements are described.