Representation of the musical instruments directivity using dodecahedron loudspeakers.

Abstract

Room-acoustical measurements in general are performed with omnidirectional sound sources. With respect to auralization, such an impulse response may not be ideal since it does not represent the situation playing an instrument in the room. To achieve the directivity of a real source (such as an instrument or human voice) with a technical sound source (a loudspeaker) requires either to copy the body and the surface velocity distribution of that particular source or to reproduce the directional pattern of the radiation using a multiple source configuration like a dodecahedron loudspeaker array with independent excitation of each transducer. The advantage of the latter method is obvious since one single source is able to provide different directivities by changing the excitation profile. To maintain the appropriate excitation of each individual transducer, different approaches can be made. The method described here uses spherical harmonics decomposition of the target radiation pattern and a subsequent calculation of the frequency dependent excitation coefficients for each transducer. The advantage of this method is a flexible and fast calculation delivering filters that can be used either for real time convolution or off-line processing of the measuring signals. To measure the instruments directivity an array with 32 microphones is used.