Consultation des notices

The modeling of wave propagation in a horn is still problematic as the limit of plane wave approximation is known but no method is proven to give accurate results. This paper proposes to evaluate the error induced by both a plane wave model and a spherical model. These models use a Transmission-Matrix Method based on either plane or quasi-spherical propagation and loaded with two different radiation impedances. This study is done on two musical instruments horns, one from a trumpet and the other from a trombone, whose geometry is known to within a tenth of millimetre. The respective inuence of both propagation and radiation is observed by comparing the input impedance measured on each of the two horns with the impedance calculated with both models. Differences between models and measurements are quantied and an extension to a whole trombone is also done. The spherical model approximates the behaviour of the horn with an improved accuracy and differences between the model and the measurement do not rise above 25 cents.