[Dixielandjazz] Slide trombones

Robert Newman bobngaye at surewest.net
Mon Mar 21 13:23:31 PST 2005

Paul -- A very good dissertation on the acoustics of brass instruments -- in 
fact all tubular wind instruments.   Very profound.    But in the case of 
the trombone, you  --  obviously accidentally, spelled CONICAL wrong.    The 
correct spelling is COMICAL.

Nobody's perfect

Signed, with great admiration

Bob Newman

----- Original Message ----- 
From: "Edgerton, Paul A" <paul.edgerton at eds.com>
To: "'Dixieland Jazz'" <dixielandjazz at ml.islandnet.com>
Sent: Monday, March 21, 2005 12:22 PM
Subject: RE: [Dixielandjazz] Slide trombones

> Time for another DJML science lesson: today's word is "parabola."
> A parabola is a conic section. That is, one can take a cone standing on 
> its
> circular base -- a trombone will do nicely -- and slice it parallel to the
> axis of the cone.  The resulting curve is called a parabola.  Anybody who
> has seen the Gateway Arch in St. Louis or watched a perfectly thrown "Hail
> Mary" pass has seen what I'm describing.  (Kids! If you try this 
> experiment
> at home, use a sharp band saw -- but ask permission first!)
> The mathematically significant feature of a parabola is that it has a 
> focal
> point.  In the case of a trombonist, the focal point is typically seated 
> at
> the bar in a short skirt.
> When a parabola is rotated through space about its axis, it forms a
> paraboloid.  One common paraboloid is a satellite dish antenna. Another is
> the reflective surface of an old-style automotive headlamp.  If a 
> trombonist
> is rotated about his axis, he gets dizzy.  The same effect is generated 
> when
> he sits at the bar next to the skirt.
> The purpose of a horn is to couple an acoustic radiator with the focal
> point, so it isn't correct to say a brass instrument's bore is parabolic.
> Now that you have now been properly educated, you can avoid making
> embarrassing mistakes like this in conversation with the skirts at the 
> bar.
> All brass instruments have bores that are conical, and most contain
> cylindrical sections to accommodate things like tuning slides.  The 
> trumpet
> and trombone, in particular, have a bore that is predominantly cylindrical
> with the conical sections being mainly in the lead pipe and bell.
> Wait a minute, I have just received new information that the primary
> definition of the word "parabolic" is "Of or similar to a parable."
> Ahem, please forget I ever mentioned the skirt at the bar.
> -- Paul Edgerton
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