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Re: Interesting case related to pitch perception

Hi Arturo :)

I don't know if this helps but looking at the spectrogram of it


it shows that the 500Hz harmonic complex is only present while the on- and the offset of the tone.

I don't know about your experiment design, but if I "remove" them by windowing the waveform so that the first 50ms and the last 100ms are silenced I still have the same pitch percept - perhaps this would be a solution?

:) stefan

Dipl.-Math./Inf. MSc Stefan Strahl
University of Oldenburg
Department of Physics
Signal Processing Group
26111 Oldenburg, Germany
Room  W2 2-247b
Phone +49 441 798 3249
EMail stefan.strahl@xxxxxxxxxxxxxxxx

Arturo Camacho wrote:
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