By the way before my physics friends correct me, what I'm calling the
linear response spectrum in the inverse of
the impedance, so when I talk of a peak (in response) this corresponds to
the minimum (in impedance).
I think I might have even called the response function the inpedance out of
casualness. But anyway X(f) = 1/Z(f), if you will.
m.
At 09:56 PM 9/16/2003 +1000, you wrote:
>Greetings.
>
>I sent the whole discussion on acoustics to Joe Wolfe. Here is his reply
>(see below).
>
>As for me, it's probably a bit like anything really, say horses. Horse
>people like to talk about horse food, horse stables, horses themselves,
>horse shoes, saddles, horse riding techniques, breeds, genealogies, and so
>forth. In general terms, in technical terms, in mystical and in mythical
>terms. Whatever. So long as it has to do with horses, it's interesting.
>More than interesting.
>It's fascinating.
>
>Best regards, Riley
>
>Sound of Bamboo
>PO Box 939
>Manly 1655 NSW Australia
>Tel: +61 (0)2 9976 6904
>Fax: +61 (0)2 9976 6905
>mobile: +61 (0)414 626 453
>www.rileylee.net
>
>
>Dear Shakuhachi list,
>
>the Acoustics Lab at the University of New South Wales has done some work
>on impedance spectra of shakuhachi and other wind instruments. Our site at
>http://www.phys.unsw.edu.au/music has a section on shakuhachi acoustics.
>We are working on a few problems related to your discussion.
>
>As scientists working in this area, obviously we think that science can
>make a contribution. We think of the instrument as a tool for making music,
>and that in some cases we hope to improve that tool. This attitude may not
>seem sufficiently respectful to shakuhachi tradition, so I apologise: it is
>an attitude that we have developed from working on occidental instruments.
>Whatever you may think of such an attitude, here are a few relevant
>observations.
>
>Making the shakuhachi with the 'optimum' impedance spectrum Z(f) is, as you
>have mentioned, an awkward problem. Not so much technically: the shakuhachi
>is one of the few wind instruments in which makers can not only take
>material out of the bore, but also put it in. And the physics needed to
>calculate the bore shape is mainly messy, not very difficult. Having a
>small number of tone-holes simplifies the calculation.
>
>For instance, one property that one might think desirable is to have the
>first two minima in Z(f) in the ratio 2:1. (Perhaps higher resonances might
>have harmonic ratios as well, but this is in general very difficult.) In
>principle, one would expect this to give not-only well tuned octaves but a
>more stable and stronger lower octave, because the first two (and sometimes
>higher) resonances of the instrument 'cooperate' with the air jet to
>produce notes in the lower register.
>
>The complication comes because the Z(f) in question should include the
>effect of the player's chin and lips, and also related properties of the
>jet. These are quite variable --indeed that is one of the chief features
>and attractions of the instrument. They are also frequency dependent, in a
>somewhat different way from the instrument. So one needs to know what the
>Z(f) of the player's embouchure is. (Awkward, but not impossible: we did
>some measurements of the Z(f) of the embouchure of players (including Riley
>Lee) for several notes.) The trouble comes in deciding which notes, and for
>how much 'meri', if I may put it that way, one would want to optimise such
>a property.
>
>For two reasons, we decided to tackle this problem first on the transverse
>(occidental) flute. One is that it is somewhat easier to make decisions
>about what ought to be optimised. Another is that a local maker of
>occidental flutes (Terry McGee in Canberra) was keen to collaborate with
>us, and the government is keen on universities collaborating with local
>makers. This is now the doctoral project of a student in the lab (Paul
>Dickens).
>
>However, we are still quite puzzled about the shakuhachi and want to return
>to that problem in the future (unless the posters on this list have solved
>the problems first).
>
>Anyone who is interested in how such calculations may be done could see
>Botros et al (2002), which downloads from
>http://www.phys.unsw.edu.au/music/publications.html
>This reports doing the calculations in the 'forwards' direction (bore to
>Z(f), rather than the inverse), but the inversion problem (making the
>backwards direction calculation) is essentially making a 'book' of the
>forwards calculation, then looking it up, finding useful areas of parameter
>space, making a new book, looking it up.... fortunately computers don't
>mind doing such mindless work.
>
>Good luck and good music
>Joe Wolfe
>Acoustics Lab, UNSW, Sydney http://www.phys.unsw.edu.au/music
>
>List subscription information is at:
>http://communication.ucsd.edu/shaku/listsub.html
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