Dear members of the list,
I am analyzing the spectrum of musical instruments in a pitch-related
study and found something that puzzles me: the spectrum of an oboe playing
the note G6 (approximately 1500 Hz pitch) contains peaks not only at
multiples of 1500 Hz but also at each multiple of 500 Hz. This was
observed in a sample taken from the University of Iowa Musical Instruments
Database (http://theremin.music.uiowa.edu/MIS.html), specifically, the 8th
note in the file "oboe.pp.C6Ab6.aiff". I do not know much about wind
instruments, but my guess is that the position used to play G6 is probably
the same used to play C5 and the only difference is the pressure in the
mouth. This could leave the harmonics of C5 alive and that is why there is
energy at multiples of 500 Hz. If someone know the reasons of this effect
please let me see the light, because it would be nice to offer an
explanation of this in my study.
As an aside, this is an interesting example of a case in which the pitch
is different from the fundamental. From the log-magnitude of the spectrum
it is very clear that the signal consists of multiples of 500 Hz (although
with boosted 3rd, 6th, 9th, etc. harmonics), and therefore, the
fundamental frequency, if any, should be considered as 500 Hz and not 1500
Hz.
Arturo