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Police whistle

  1. May 21, 2005 #1
    What effect does the sphere inside of a police whistle have on its resultant sound?
  2. jcsd
  3. May 21, 2005 #2
    I believe it intensifies the sound?

    The police whistle I think, is a variant of TIN WHISTLE, which is just an instrument that produces only 2-Octave sounds?

    The principle and dynamics of Tin whistle's, can occur when opening a sunroof of a moving car for instance.

    Here is a link that explains a little more:http://en.wikipedia.org/wiki/Whistle

    I am going to assume that you are delving into Particle-In-A-Box and the Police Whistle is thus an analogy of sorts?

    Afterthought..maybe the input and output of a spherical Blackhole? :cool:
    Last edited: May 21, 2005
  4. May 22, 2005 #3


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    If not, then I will go back to the original 'pea-whistle'. The whole point of having the 'pea' or other spherical body in the whistle is to alter the airflow and thus produce a tone. Think of it as a person doing a '2 finger whistle'.
  5. May 22, 2005 #4
    Pea whistle it is. What is the acoustic (mathematical) sense for using the pea?
  6. May 22, 2005 #5
    I got the following information from this link http://www.kenaston.org/History/RefereeWhistle.html [Broken]

    In a pea whistle, the air stream enters through the mouthpiece as shown (1). It hits the bevel (2), and splits outwards into the air, and inwards filling the air chamber (3) until the air pressure inside the chamber is so great, it pops out of the sound hole, making room in the chamber for the whole process to start over again. The pea (4) gets forced around and around and interrupts the flow of air and changes the rate of air packing and unpacking inside the air chamber. This creates the sound of the whistle warble.

    The air stream enters through the whistle's mouthpiece as shown.

    The air inside a whistle chamber packs and unpacks 263 times every second to make the note middle-C. The faster the packing and unpacking is, the higher- pitched the sound the whistle creates.
    Last edited by a moderator: May 2, 2017
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