Numerical study on the function of tone holes of a recorder like instrument from the viewpoint of the aerodynamic sound theory

Abstract

We have investigated properties of tone holes of a small recorder like instrument by using compressible Large-eddy simulation (LES), which reproduces fluid flow and acoustic field, simultaneously. When an acoustic flow of strong sound pressure passes through the junction between a tone hole and the main body of the bore, vortex shedding occurs, which induces unpleasant noises due to re- radiation of aerodynamics sound from the vortices. We have succeeded in reproducing this process and attempted to explain its mechanism from aerodynamic sound theory. We have also investigated how the position of the pad of a key above a tone hole, i.e., the distance between the pad and the top of the tone hole, affects the pitch of the excited wave in the pipe. Furthermore, we attempt to numerically reproduce the function of tone holes, namely change of notes. Opening and closing tone holes change the topology of bore geometry, which yields a moving boundary problem accompanied by topological change of numerical grids. We have developed a LES solver resolving the moving boundary problem and are planning to apply it to the problem of opening and closing tone holes.