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*Variable pitch whistle - a whistle containing an internal piston available for changing pitch. This whistle type could be made to sound like a siren or to play a melody. Often called a fire alarm whistle, wildcat whistle, or mocking bird whistle.
*Toroidal or Levavasseur whistle - a whistle with a torus-shaped (doughnut-shaped) resonant cavity paralleling the annular gas orifice, named after Robert Levavasseur, its inventor. Unlike a conventional whistle, the diameter (and sound level) of a

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