Modeling the radiation of modern sound reinforcement systems in high resolution
- Modellierung der Abstrahlung moderner Beschallungsanlagen in hoher Auflösung
Feistel, Stefan; Vorländer, Michael (Thesis advisor)
Berlin : Logos-Verl. (2014)
Dissertation / PhD Thesis
In: Aachener Beiträge zur technischen Akustik 19
Page(s)/Article-Nr.: V, 207 S. : Ill., graph. Darst.
Zugl.: Aachen, Techn. Hochsch., Diss., 2013
Starting from physical theory, a contemporary novel framework is developed for the acoustic simulation of sound radiation by loudspeakers and sound reinforcement systems. A variety of own measurements is presented. These agree very well with the predictions of the computer model considering practical uncertainty requirements. First, small sound sources are discussed. Such a source is used at receive distances much larger than its characteristic dimension. A theoretical foundation is derived for the accurate reproduction of simple and multi-way loudspeakers using an advanced point source model that incorporates phase data. After that the practical implementation of this so-called CDPS model is presented including measurement requirements and the newly developed GLL loudspeaker data format. Subsequently the novel model is validated in detail by means of a number of different measurement results. In the second part, larger systems are analyzed such as line arrays where the receiver is often located in the near field of the source. It is shown that theoretically any line source can be decomposed into smaller elements with a directional characteristic. This approach allows modeling the performance of the complete line source in both near and far field as long as the considered receive location is in the far field of the elementary sources. Several comparisons of measured line arrays display good agreement with predicted behavior and underline the superiority of this model compared to existing simulation methods. At the end theoretical methods and measured results are used to show for the first time that the influence of production variation among supposedly identical cabinets has a measurable but small effect on the overall performance of a line array. The last part of this work deals with the consequences of fluctuating environmental conditions, such as wind and temperature, on the propagation of sound. In the context of this work, it is of particular interest to consider the coherent superposition of signals from multiple sources at the receive location. For this purpose a novel theoretical model is developed that allows predicting the mean variation of the propagation delay of the sound wave as a function of the statistical properties of the environmental parameters. Measurements of these properties as well as of the sound travel time are consistent with corresponding modeling results. Finally, it is discussed how the average total sound pressure level of a line array or loudspeaker arrangement is affected by the random variation of propagation delays. A part of this work was distinguished with the AES Publications Award 2010. Parts of the proposed data format have been incorporated into the international AES56 standard.