A Hybrid method is proposed for prediction of bio-fluid sounds at very low Mach numbers. The unsteady hydrodynamic flow field is computed by the incompressible Navier-Stokes equations (INS), while the sound field is obtained by solving the linearized perturbed compressible equations (LPCE) with sound sources represented by a total derivative of the hydrodyanmic pressure, DP/Dt. With the present INS/LPCE hybrid method, the vocal sound in human larynx and the buzz sound of bumblebee are computed with more clear understanding on the sound generation processes associated with their characteristic motions such as the self-sustained oscillatory motions of the vocal folds and the figure-eight motion of the flapping wings. A bio-fluid sound is the sound generated by fluid motions coupled with a biological body in motions; for example, phonation in human larynx, buzz sound of flapping wings, etc. Understanding of the bio-fluid sound is important not only for fundamental studies but also for its bio-mimetic applications. In many cases, however, sound generation processes are not fully understood yet.
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