Model Scale Measurements of the Sound Emissions of Supermarkets

Frequently local supermarkets are built within residential areas. Annoying noise is generated as delivery trucks unload their goods. During the planning phase of new supermarkets, the protection of the inhabitants from sound immissions must be proven by numerical predictions. The improvement of these prediction methods has been supported by measurements on a model scale.

Noise immissions caused by delivery trucks unloading their goods are very annoying to residents due to the significant characteristics of the noise produced, particularly in highly populated residential areas with local retailers. For environmental noise protection, noise immissions have to be predicted by calculations during the planning phase of new supermarkets. Standard software is based on the ray model of sound propagation, as are the corresponding guidelines. Ray models become deficient if physical phenomena like diffraction and multiple reflections gain in importance due to the geometric complexity of the situation. These deficiencies usually appear clearly in the consulting business. Consequently, immissions and the efficiency of noise protection procedures cannot be predicted exactly.

The development of an improved prediction method by the ”Institut für Angewandte Mechanik” of the ”Technische Universität Braunschweig” is funded by the ”Deutsche Bundesstiftung Umwelt”. In this project, simulations based on wave models for sound propagation showed significant differences compared to the results of two ray based models. Neither of the two ray based models (point source or distributed sound source) could be favored from this. Further points of reference were necessary.

A cooperation with the PTB was started to perform measurements in a model scale of 1:8. The figure shows the set-up built of medium density fiberboard inside a hemi-anechoic room. For reasons of explanation, the wooden segments were superimposed with transparent diagrams of a truck and a supermarket facade. The completed measurements will be used to evaluate and to subsequently improve the computation models.

Figure 1: Measurements in a model scale of 1:8 in a hemi-anechoic room

Contact person:

Martin Schmelzer, Dept 1.7, WG 1.72, email: martin.schmelzer@ptb.de