Abstract: This paper introduced the mechanism of the aerodynamic sound through some examples. They are the sound generated by steady but inhomogeneous flow past rigid surfaces; the aeolian tones generated by steady flow about a small obstacle; the edgetone and the turbulent jet noise. The sound power and efficiencies of these different aerodynamic sound have been compared with each other. An understanding to these mechanisms is helpfull to the control of the aerodynamic noise.