text: does anybody know how a whistle works? i mean like the child's toy type of whistle the air blown comes out of a small opening.  at the opening the pressure drops suddenly,  the air in the small cylindrical vessel below the opening rushes to the reduced pressure spot.  the surrounding air also rushes to the spot.  but the equilibrium of pressure is attained only after some vibrations. (just like a pendulum comes to stop after some vibrations.  but all these happen for a single burst of air blow.  sound is the compressions and rarefactions of air.  when we continuously blow air, the air is made to vibrate with  different frequencies  which depends upon the volume of air made to vibrate.  thus the whistle sound is heard.