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Looper's Delight
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--- Matthias Grob <matthias@grob.org> wrote: > > > >The spectrogram allows us to see, in a scrolling chart, over time in > >the horizontal axis, the frequency components in the vertical axis, > >with the amplitude of each component indicated by shading. The > lowest > >tone recorded was about 390 hz, approximately a G. The first > overtone > >was at about 1070 hz, the next at about 1950 hz. These measurements > >are +/5.4 hz with the scale and tool used. > > hm,,, for me overtones are multiples... > > >We attempted to match the tone by ear, to a synth patch that had > >fundamental and 2 harmonics (390hz,1170hz, 1950hz , fund, 3rd and > 5th > >harmonics). We compared the audibly matched synth tone to the bowls > >tone in the spectrogram. The fundamentals matched in frequency. > What > >we heard as tones in the bowl, matched what we heard on a minimal > >overtone synth oscillator. These sounds differ by the first > overtone > >frequency. The synth has 1170hz (3rd harmonic) and the bowl has > about > >1070hz which is about 2.74 times the fundamental (390hz). > > may this mean that 390 is not the fundamental? > Then again, I cannot find a fundamental with overtones 390 and > 1070... > I can easily imagine several fundamentals, so 390 and 1070 could be > independent vibrations (axial-radial, for esample). > But why is the third harmonic 1170 present? Did the 1070 "eat" it? > > More even I wonder now how they select the bowls: Could yours be a > good one because the 5th harmonic appears cleanly... or a cheap one > because the 3rd does not? :-) > > >We found no illusion between perceived pitch, and measure pitch with > >the 2 types of sounds. The beats in the rubbed bowl do change the > >character of the sound dramatically, however. > > I am not sure I understand what the beating sounds like... > Is it a subharmonic maybe? > Interference between the stick movement and some fundamental? I used the word beating, as the effect was rather like two tones very close in frequency to each other, but not quite (say 1hz to 8 hz difference). We hear this as a pulsation of amplitude as they go in and out of phase, and reinforce and cancel each others output at a rate of 1hz to 8hz. To me it sounds like "yun yun yun yun". It is amplitude modulation (of the tones of the bowl). I find it interesting that this frequency range (of the pulsing) covers the lower end of the brain wave frequencies that are known to be very deep relaxation, meditation, and altered states of conscienceness. Could this entrain the brain to these frequencies like flashing light can? So, what I heard and see on the spectrogram is the amplitude of the tones pulsing, at a 1hz to 8hz rate. Somehow the stick rate influences it, maybe as it hits nodes and antinodes of the movement (wave) on the edge of the bell (this is wild, pure speculation). Lindsays' reference (http://www.mmk.ei.tum.de/persons/ter.html) to the Ernst Terhardt has some great research topics. See http://www.mmk.ei.tum.de/persons/ter/top/strikenote.html for an interesting article on the part-tone series of bells, and that they do not fit the normal harmonic series (and what that does to human interpretation of pitch). My use of the word 'overtones' seems to be confusing. I was not sure what to call these nonharmonic part-tones. I called them overtones because they are over (higher in freq) the lowest tone produced (what I considered the fundamental). Typically part-tones of musical instruments are harmonic (multiples), except in clangorous tones (like bells) where some partials appear out of place. bret __________________________________________________ Do You Yahoo!? Yahoo! Messenger - Talk while you surf! It's FREE. http://im.yahoo.com/