Assessment of methods for determining field‐equivalent sound levels from real‐ear and manikin measurements Free

The usual method of measuring noise with a sound‐level meter at the position of the exposed person, but with the person absent, is not applicable for sound sources placed close to the ears. For measurement of the noise emission from such sources, the coupling between the sound source and the ear must be similar to that of the real life situation. This can be achieved by using the microphone in real ear technique (the MIRE technique) or the manikin technique as described in the upcoming ISO 11904, parts 1 and 2, respectively. For evaluation and comparison with traditional criteria, the measured ear or manikin sound‐pressure levels are subsequently converted into either free‐field or diffuse‐field equivalent sound‐pressure levels. The uncertainty of the final result depends on the method used. For the MIRE technique, the uncertainty is mainly related to the statistical uncertainty as determined by the variation between humans and the number of subjects used. For the manikin technique, the uncertainty is mainly related to the deviation of the manikin’s acoustical characteristics from those of humans. The paper presents an overview of the methods and examples of practical results.