| Résumé |
The control of directivity represents a new stake in the reproduction of the sound sources by electroacoustics devices. In a larger frame, this research direction fits in the field of studies devoted to the spatialization domain, from a technological and perceptive point a view. A previous work proposed a general method for reproducing the acoustical field radiated by a source, using a multichannel device controlled by digital signal processing. The general principle is to approximate a given directivity pattern by linear combination of the fields radiated by a set of loudspeakers laid out on the faces of a polyhedron. This work, undertaken in parallel using simulations and prototype developments, showed the scientific and perceptive interest of the process Ongoing studies are devoted, on the one hand, to the general improvement of the system (particularly, its bandwidth) and, on the other hand, to the optimization of the directivity control. This one can be measured in terms of perceptive relevance and real time processing that are significant characteristics when considering the integration of the method in a musical context. The directivity control rests on the preliminary constitution of a set of basic directivities – namely the first spherical harmonics – with which it is possible to tune the cardioïcity and the three-dimensional orientation of the directivity pattern. Moreover, for the simulation of musical instruments, it appears significant to tune independently the spatial and spectral characteristics. In particular, listening in a room tends to average the spectral contributions radiated by the instrument in the different directions. For that, an analysis/synthesis method of the power spectrum is developped to allow the automatic design of a correction filter to be applied on near field recording of the instrument. The results will be discussed by considering reproduction examples of several instruments (harpsichord, flute, human voice,…). |
