OT: Spacial aliasing (or so they claim)

On Mon, 15 Aug 2011 08:03:48 -0700 (PDT), Jerry Avins <jya@ieee.org> wrote: >A beautiful demo of many oscillators with a common sub-period: >http://tinyurl.com/3ee2eya > >Jerry >-- >Engineering is the art of making what you want from things you can get. That's pretty cool, and the "aliasing" is easily seen as the spatial frequency sweeps through and back. This one isn't quite the same, but has a similar aesthetic: http://www.youtube.com/watch?v=vh2a4a6JPM8 Eric Jacobsen http://www.ericjacobsen.org http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php

On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: > A beautiful demo of many oscillators with a common sub-period:http://tiny= url.com/3ee2eya > > Jerry > -- > Engineering is the art of making what you want from things you can get. That's pretty F***in' cool! I wonder how long it took to "tune" it?

>On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >> A beautiful demo of many oscillators with a common sub-period:http://tiny= >url.com/3ee2eya >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. > >That's pretty F***in' cool! I wonder how long it took to "tune" it? I imagine that tuning was unnecessary. Its just a matter of careful assembly, to keeps the balls in a nice straight line. I wonder how much practice it took to get a clean release of the entire row, though? :-)

On Mon, 15 Aug 2011 19:04:41 -0500, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >>On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >>> A beautiful demo of many oscillators with a common >sub-period:http://tiny= >>url.com/3ee2eya >>> >>> Jerry >>> -- >>> Engineering is the art of making what you want from things you can get. >> >>That's pretty F***in' cool! I wonder how long it took to "tune" it? > >I imagine that tuning was unnecessary. Its just a matter of careful >assembly, to keeps the balls in a nice straight line. I wonder how much >practice it took to get a clean release of the entire row, though? :-) Probably not much. It looks like the technique using the board is pretty common looking at some similar vids on YT. http://www.youtube.com/watch?v=1M8ciWSgc_k&feature=related Eric Jacobsen http://www.ericjacobsen.org http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php

On Aug 15, 8:04=A0pm, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > >On Aug 15, 11:03=3DA0am, Jerry Avins <j...@ieee.org> wrote: > >> A beautiful demo of many oscillators with a common > > sub-period:http://tiny=3D > > >url.com/3ee2eya > > >> Jerry > >> -- > >> Engineering is the art of making what you want from things you can get= .. > > >That's pretty F***in' cool! I wonder how long it took to "tune" it? > > I imagine that tuning was unnecessary. Its just a matter of careful > assembly, to keeps the balls in a nice straight line. I wonder how much > practice it took to get a clean release of the entire row, though? :-) I think the tuning wasn't easy. The period is proportional to the square root of length, but the effective length is the distance from the support attachment to the center of percussion, a point somewhat beyond the center of mass, and closer to it with the longer strings. It is easy to get close with a little calculation, but that's like trying to tune a guitar with a tensimeter. Jerry -- Engineering is the art of making what you want from things you can get.

>On Mon, 15 Aug 2011 19:04:41 -0500, "steveu" ><steveu@n_o_s_p_a_m.coppice.org> wrote: > >>>On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >>>> A beautiful demo of many oscillators with a common >>sub-period:http://tiny= >>>url.com/3ee2eya >>>> >>>> Jerry >>>> -- >>>> Engineering is the art of making what you want from things you can get. >>> >>>That's pretty F***in' cool! I wonder how long it took to "tune" it? >> >>I imagine that tuning was unnecessary. Its just a matter of careful >>assembly, to keeps the balls in a nice straight line. I wonder how much >>practice it took to get a clean release of the entire row, though? :-) > >Probably not much. It looks like the technique using the board is >pretty common looking at some similar vids on YT. > >http://www.youtube.com/watch?v=1M8ciWSgc_k&feature=related Does that "probably not much" thing work with other stuff I see people doing on youtube, like playing guitar or piano at breakneck speed? :-\ Steve

On Aug 15, 9:47=A0pm, Jerry Avins <j...@ieee.org> wrote: > On Aug 15, 8:04=A0pm, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > > > > > > > >On Aug 15, 11:03=3DA0am, Jerry Avins <j...@ieee.org> wrote: > > >> A beautiful demo of many oscillators with a common > > > sub-period:http://tiny=3D > > > >url.com/3ee2eya > > > >> Jerry > > >> -- > > >> Engineering is the art of making what you want from things you can g= et. > > > >That's pretty F***in' cool! I wonder how long it took to "tune" it? > > > I imagine that tuning was unnecessary. Its just a matter of careful > > assembly, to keeps the balls in a nice straight line. I wonder how much > > practice it took to get a clean release of the entire row, though? :-) > > I think the tuning wasn't easy. The period is proportional to the > square root of length, but the effective length is the distance from > the support attachment to the center of percussion, a point somewhat > beyond the center of mass, and closer to it with the longer strings. > It is easy to get close with a little calculation, but that's like > trying to tune a guitar with a tensimeter. > > Jerry > -- > Engineering is the art of making what you want from things you can get.- = Hide quoted text - > > - Show quoted text - At school, we have a large version of Newton's Cradle with about 15 balls. Each ball is suspended from two strings just like in the video, and I know from experience that setting each to the correct height takes some work and with the Cradle, they all just simply have to be the same length. With these pendula one can use an optical timer for each one but even it still must be a "bit fiddly" setting all of the lengths to the correct periods. Clay

On Mon, 15 Aug 2011 08:03:48 -0700 (PDT), Jerry Avins <jya@ieee.org> wrote: >A beautiful demo of many oscillators with a common sub-period: >http://tinyurl.com/3ee2eya > >Jerry >-- >Engineering is the art of making what you want from things you can get. BTW, just saw this today, and while mostly unrelated it is a neat roundabout way to demonstrate Fourier Series: http://www.youtube.com/watch?v=muCPjK4nGY4 Eric Jacobsen http://www.ericjacobsen.org http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php

On Mon, 15 Aug 2011 23:11:51 -0500, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >>On Mon, 15 Aug 2011 19:04:41 -0500, "steveu" >><steveu@n_o_s_p_a_m.coppice.org> wrote: >> >>>>On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >>>>> A beautiful demo of many oscillators with a common >>>sub-period:http://tiny= >>>>url.com/3ee2eya >>>>> >>>>> Jerry >>>>> -- >>>>> Engineering is the art of making what you want from things you can >get. >>>> >>>>That's pretty F***in' cool! I wonder how long it took to "tune" it? >>> >>>I imagine that tuning was unnecessary. Its just a matter of careful >>>assembly, to keeps the balls in a nice straight line. I wonder how much >>>practice it took to get a clean release of the entire row, though? :-) >> >>Probably not much. It looks like the technique using the board is >>pretty common looking at some similar vids on YT. >> >>http://www.youtube.com/watch?v=1M8ciWSgc_k&feature=related > >Does that "probably not much" thing work with other stuff I see people >doing on youtube, like playing guitar or piano at breakneck speed? :-\ > >Steve I think that hand-held board launch technique at the beginning of the vid isn't very comparable to a skilled musician. Eric Jacobsen http://www.ericjacobsen.org http://www.dsprelated.com/blogs-1//Eric_Jacobsen.php

On Mon, 15 Aug 2011 18:47:26 -0700 (PDT), Jerry Avins <jya@ieee.org> wrote: >On Aug 15, 8:04�pm, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >> >On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >> >> A beautiful demo of many oscillators with a common >> >> sub-period:http://tiny= >> >> >url.com/3ee2eya >> >> >> Jerry >> >> -- >> >> Engineering is the art of making what you want from things you can get. >> >> >That's pretty F***in' cool! I wonder how long it took to "tune" it? >> >> I imagine that tuning was unnecessary. Its just a matter of careful >> assembly, to keeps the balls in a nice straight line. I wonder how much >> practice it took to get a clean release of the entire row, though? :-) > >I think the tuning wasn't easy. The period is proportional to the >square root of length, but the effective length is the distance from >the support attachment to the center of percussion, a point somewhat >beyond the center of mass, and closer to it with the longer strings. >It is easy to get close with a little calculation, but that's like >trying to tune a guitar with a tensimeter. > >Jerry Hi Jer, I agree with you and Clay. I'll bet the 'tuning' took quite a while. [-Rick-]

Rick Lyons <R.Lyons@_bogus_ieee.org> wrote: (snip on pendulum waves) >>> I imagine that tuning was unnecessary. Its just a matter of careful >>> assembly, to keeps the balls in a nice straight line. I wonder how much >>> practice it took to get a clean release of the entire row, though? :-) The one I saw didn't have all that good a start. >>I think the tuning wasn't easy. The period is proportional to the >>square root of length, but the effective length is the distance from >>the support attachment to the center of percussion, a point somewhat >>beyond the center of mass, and closer to it with the longer strings. >>It is easy to get close with a little calculation, but that's like >>trying to tune a guitar with a tensimeter. > I agree with you and Clay. I'll bet the 'tuning' took quite a while. My thought while watching was to tune each to resonance. That is, excite the system at the desired frequency, and adjust the length until it reaches that frequency. For a period of 1s, and desire to be not too far off after 60s, the periods have to be somewhat better than 1% accurate. Without trying, I don't know how hard that it to do. -- glen

On Aug 19, 4:02=A0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote: ... > My thought while watching was to tune each to resonance. =A0That is, > excite the system at the desired frequency, and adjust the length > until it reaches that frequency. =A0For a period of 1s, and desire > to be not too far off after 60s, the periods have to be somewhat > better than 1% accurate. =A0Without trying, I don't know how > hard that it to do. =A0 Each change of tuning involves retying two knots, keeping the strings nearly equal lengths. I would find it hard. Jerry -- Engineering is the art of making what you want from things you can get.

>On Aug 19, 4:02=A0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote: > > ... > >> My thought while watching was to tune each to resonance. =A0That is, >> excite the system at the desired frequency, and adjust the length >> until it reaches that frequency. =A0For a period of 1s, and desire >> to be not too far off after 60s, the periods have to be somewhat >> better than 1% accurate. =A0Without trying, I don't know how >> hard that it to do. =A0 > >Each change of tuning involves retying two knots, keeping the strings >nearly equal lengths. I would find it hard. > >Jerry >-- >Engineering is the art of making what you want from things you can get. > Don't use knots. They make life very hard, as the shape of the know substantially affects tuning. Some form of simple clamp will work out much easier to tune, as long as you can avoid clumsy people tugging the cord out of place. A simple tight slot may be enough. Steve

On Aug 20, 11:35=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > >On Aug 19, 4:02=3DA0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrot= e: > > > =A0... > > >> My thought while watching was to tune each to resonance. =3DA0That is, > >> excite the system at the desired frequency, and adjust the length > >> until it reaches that frequency. =3DA0For a period of 1s, and desire > >> to be not too far off after 60s, the periods have to be somewhat > >> better than 1% accurate. =3DA0Without trying, I don't know how > >> hard that it to do. =3DA0 > > >Each change of tuning involves retying two knots, keeping the strings > >nearly equal lengths. I would find it hard. > > >Jerry > >-- > >Engineering is the art of making what you want from things you can get. > > Don't use knots. They make life very hard, as the shape of the know > substantially affects tuning. Some form of simple clamp will work out muc= h > easier to tune, as long as you can avoid clumsy people tugging the cord o= ut > of place. A simple tight slot may be enough. The video shows no evidence of clamps that I can see. Jerry -- Engineering is the art of making what you want from things you can get.

>On Aug 20, 11:35=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >> >On Aug 19, 4:02=3DA0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrot= >e: >> >> > =A0... >> >> >> My thought while watching was to tune each to resonance. =3DA0That is, >> >> excite the system at the desired frequency, and adjust the length >> >> until it reaches that frequency. =3DA0For a period of 1s, and desire >> >> to be not too far off after 60s, the periods have to be somewhat >> >> better than 1% accurate. =3DA0Without trying, I don't know how >> >> hard that it to do. =3DA0 >> >> >Each change of tuning involves retying two knots, keeping the strings >> >nearly equal lengths. I would find it hard. >> >> >Jerry >> >-- >> >Engineering is the art of making what you want from things you can get. >> >> Don't use knots. They make life very hard, as the shape of the know >> substantially affects tuning. Some form of simple clamp will work out muc= >h >> easier to tune, as long as you can avoid clumsy people tugging the cord o= >ut >> of place. A simple tight slot may be enough. > >The video shows no evidence of clamps that I can see. I can't see any knots, either. The strings seem to got into small holes in a U channel at the top. If I were doing this I'd try small bulldog clips, or maybe even small clothes pegs, in that channel, rather than knots. Steve

On Aug 21, 1:50=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > >On Aug 20, 11:35=3DA0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote= : > >> >On Aug 19, 4:02=3D3DA0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> > wrot=3D > >e: > > >> > =3DA0... > > >> >> My thought while watching was to tune each to resonance. =3D3DA0Tha= t > is, > >> >> excite the system at the desired frequency, and adjust the length > >> >> until it reaches that frequency. =3D3DA0For a period of 1s, and des= ire > >> >> to be not too far off after 60s, the periods have to be somewhat > >> >> better than 1% accurate. =3D3DA0Without trying, I don't know how > >> >> hard that it to do. =3D3DA0 > > >> >Each change of tuning involves retying two knots, keeping the strings > >> >nearly equal lengths. I would find it hard. > > >> >Jerry > >> >-- > >> >Engineering is the art of making what you want from things you can > get. > > >> Don't use knots. They make life very hard, as the shape of the know > >> substantially affects tuning. Some form of simple clamp will work out > muc=3D > >h > >> easier to tune, as long as you can avoid clumsy people tugging the cor= d > o=3D > >ut > >> of place. A simple tight slot may be enough. > > >The video shows no evidence of clamps that I can see. > > I can't see any knots, either. The strings seem to got into small holes i= n > a U channel at the top. If I were doing this I'd try small bulldog clips, > or maybe even small clothes pegs, in that channel, rather than knots. That seems good. Jerry -- Engineering is the art of making what you want from things you can get.

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