Although the acoustic radiation of common loudspeaker systems can be easily measured using modern measurement techniques, the process requires free-field conditions that may be difficult to satisfy. Large anechoic rooms are very expensive and outdoor measurements are subject to uncontrollable weather conditions. This paper proposes the use of the radiation mode (RM) method to estimate the frequency response and directivity pattern of loudspeaker systems. The underlying theory and method principle are first described and then assessed in both an anechoic room and large non-anechoic hall by measuring four loudspeaker systems with different radiation patterns. Results show a satisfactory level of accuracy for the proposed method across all sources tested and both measurement rooms, especially when considering the reduced number of measurement points needed. These examples are then complemented with a preliminary parametric study based on the simulation of a tall system, namely a line array for which standard measurement techniques are not applicable. More specifically, the influences of identification point locations, noise, and RM series truncation are all investigated. The output of these simulations illustrates the potential of this method to characterize sound sources that cannot be measured using classical means.
https://www.aes.org/e-lib/browse.cfm?elib=19891
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