Re: Interesting case related to pitch perception

[Alastair Disley <aldisley@xxxxxxxxx>]

I have a possible answer, but first I wanted to share an equivalent L/3 example in the world of pipe organs.

Most flue organ pipes are open at the top and speak their fundamental frequency.  Stopped pipes are capped at the top which gives the same fundamental frequency for a pipe half as long, but with greatly reduced even harmonics.

There exists, however, a class of organ pipes known as harmonic pipes, usually harmonic flutes.  These are voiced to speak at the second harmonic rather than the fundamental.  These pipes are open, and sometimes have a hole half-way down the pipe to encourage development of a node, but this is not always necessary.

So much for the background.  A very few organs, typically early 20th century, have a stop known as the Zauberflöte (very occasionally translated to Flauto Magico or Magic Flute) which is a stopped harmonic pipe.  As a stopped pipe has no even harmonics at significant amplitudes, the pipe speaks at the third harmonic.

However I think this may be an overly complex explanation in this case.  Higher notes on an oboe appear to have a great many different possible fingerings, at least one of which is the same for C5 and G6, but with the addition of an octave key.  It is therefore entirely possible that there is a trace of C5 in G6, especially at the transients when the pressure is increasing or decreasing.  It would probably be interesting in this case to discover what fingering was used.  But as the oboe is conical bored and thus potentially uses all the harmonic series to achieve the notes in its range, it could be expected that G6 or C6 might have a brief "blip" of C5 depending on their fingering - particularly with beginner players!

This "phantom" presence of the fundamental of which you are playing a harmonic will of course vary from note to note and fingering to fingering, possibly even instrument to instrument, as the shape of the bore and placement of holes will affect development of a fundamental frequency - for example there may be a hole at an antinode or thereabouts on one fingering, but not another.

Caveat: I am not an oboist, nor an expert in this area.  These are just my thoughts.

Al

(Dr Alastair Disley, Audio Lab, Dept of Electronics, University of York, UK)




      ___________________________________________________________
Yahoo! Answers - Got a question? Someone out there knows the answer. Try it
now.
http://uk.answers.yahoo.com/