[modeleng] Re: Steam pressure/velocity question

At 12:09 AM 6/25/05 +0800, you wrote:
>Harry is correct, in that the height of the opening, determines the
>intensity (volume) and (to some degree) the tone of the note. The final
>decider of the note that a whistle makes is the length of the bell.

      Phill is correct (per the terms of our mutual affirmation agreement)
in that for any given vibrating column of air (inside the bell) there is
one frequency or "note."  The adjustments Phill describes may sharpen or
flatten the note slightly but any given bell volume will produce only one
note.  Adjusting the throat opening (the seperation between the steam slot
and the bell edge) through its entire range will take you from no-tone
(just wheezing, gurgling, etc), to a full-thoated tone, to no-tone again.
The sharps or flats are usually appear just on either side of the point at
which you get the fullest-throated tone.
      Most often the cause of a poor sounding whistles is that they have
not been properly adjusted for the pressure (or the medium - air or steam.)
 In addition to that, a whistle is a musical instrument and as with most
musical instruments the smallest variation in material size, thickness,
weight, quality, etc, will affect the tone in some way.  For instance I
have found that assuming all other specifications are equal, there is a
descernable difference in the tones of whistles with bells made from cast
brass or bronze, or even a heavy walled tubing, and those made with a
thin-walled brass tubing.
     The wrapping of shim around the bell that Phill mentioned served to
increase the volume of the bell, thus elongating the vibrating column of
air, thus lowering the note.

Regards,
Harry

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