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The Shape of Trumpet
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Question:
I am a student ho is doing a research on the shape of trumpet and
its relationship with sound wave. Especially, the effect of bell
and the mouthpipe. If anyone knows the secret of these questions
Replies:
As a resonator, so to speak, a trumpet is a closed end pipe. Think
about it. As soon as you put your lips up to the mouthpiece you have
closed off one end of the pipe. According to standard acoustic theory
a closed end cylindrical pipe will produce only the odd multiples of the
fundamental pitch of the pipe. Obviously this would exclude octaves,
which follow powers of two multiples of the fundamental pitch of the pipe.
Now this is obviously not the case for a trumpet. Its overtone series
follows all of the integer multiples, which includes the octaves. If
a trumpet is a closed end pipe how does this happen? It is not cylindrical!
Okay, trumpets are often called cylindrical bore instruments, but that is
misleading. Only a small section of any trumpet is truly cylindrical.
In fact most modern trumpets have gently tapered leadpipes. Now, of course,
the most non-cylindrical part of the horn is the bell and mouthpiece. The
fact that these sections are tapered so greatly changes the acoustics of
the so-called cylindrical overtone series. More and more partials, as they
are called come into existence as the taper of the mouthpiece and bell
become more significant. In fact, the simple addition of a tapered
mouthpiece to a cylindrical pipe can make it sound bugle-like. For more
information see the July 1973 edition of Scientific American. There is
an excellent article in there by the late Arthur Benade on the Physics
of Brasses. It is quite technical and accurate. Also, look into the
writings of Dr. Thomas Rossing from Northern Illinois University. He
is considered one of the foremost experts on musical physics.
Chapter Two: There is a gentelman on this bbs system who is a
brilliant brasswind machinist , designer, builder and guru. His
name is Wayne Tanabe. Try contacting him through his mailbox on this
system. Because he will be looking at this subject a little differently
he might be able to give you some insight into your question.
--Nick P. Drozdoff--
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Update: June 2012
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