  Total computational costs of scientific simulations are analyzed between
direct numerical simulations (DNS) and multiphysics simulations (MPS) for sound
generation in musical instruments. In order to produce acoustic sound by a
turbulent flow in a simple recorder-like instrument, compressible fluid dynamic
calculations with a low Mach number are required around the edges and the
resonator of the instrument in DNS, while incompressible fluid dynamic
calculations coupled with dynamics of sound propagation based on the
Lighthill's acoustic analogy are used in MPS. These strategies are evaluated
not only from the viewpoint of computational performances but also from the
theoretical points of view as tools for scientific simulations of complicated
systems.
