Prediction of noise in workrooms including extended sources, directivity of radiation, and screening

Abstract

For many years the mirror image method has been used to calculate noise levels in workrooms. Fittings are taken into account by a fitting density defined by Kuttruff and extended to this application by Jovicic. In a research program financed by BAUA Dortmund it was examined how directivity of radiation and screening can be integrated. A removable screen was installed in different halls and it measured the sound distribution in the shadow region, which was produced by a uniformly radiating loudspeaker radiating white noise. Calculation of the same situation by taking into account screening showed that only low orders of reflection are influenced by the screen. This gives the necessary information for a modification of software programs to include screening. Similar to this procedure, a loudspeaker with high directivity was used as source with known emission to measure sound decay curves in workrooms. The same situation was calculated by mirroring the complete directivity of the source. Measured and calculated levels are in good agreement. With these techniques the German standard VDI 3760 for noise calculation in rooms can be improved in the next years.