List, I thought that I was sending this to the list but it went to Sarah Fox only. So, I'm forwarding it to the list. Sorry for the funny formatting. Phil F On Sun, 17 Nov 2002 17:01:26 -0500 Sarah Fox <sarah@gendernet.org> wrote: > Hi Phil, > > > 3. If longitudinal vibrations can pass the > bridge, it seems to me that > they > > can just as easily pass the aliquot... > > Actually every contact point would be a sound > reflection point, resulting > from an abrupt impedance differential. If > we're talking about compression > waves in the string, which it appears is the > implication, the free resonant > frequency between any two contact points would > be half of the speed of sound > through spring steel (not through air), divided > by distance. It would be > *incredibly* high (bat frequencies and beyond, > not dog frequencies), and it > would only be tunable by moving contact points > (assuming the spring constant > is indeed constant -- or approximately so). > You suggest the sound would > stop at the hitch pin. It would not. That is > only another contact point. > It would travel into the plate and beyond. It > would also have a difficult > time coupling into the bridge, except by > rocking it. Two comments or questions here: 1. If the sound is reflected at contact points then it should be possible to tune the rear duplex longitudinal frequency by moving the aliquot, as CFT seemed to believe. Would you say that this is correct? 2. If longitudinal vibration in the speaking length is reflected at the bridge what would cause a longitudinal vibration in the rear duplex? 3. If these frequencies are so high that we can't hear them is there a point in doing tuning of the rear duplex for the longitudinal mode? > > Personally, the importance of longitudinal > vibrations doesn't seem very > probable to me. It is easy enough to see how > transverse vibrations are > coupled into duplex strings from vibrations in > the bridge, irrespective of > what Mr. Steinway might have claimed to the > contrary. Why invoke mysterious > ultrasonic longitudinal vibrations? Just > because Mr. Steinway got a patent > doesn't mean he understood the acoustics of his > invention. Sacrilege. <G> > > In the end, could it be that the biggest > benefit of a tuned duplex scale is > the "freeing up" of the vibrations of the > strings and bridge by eliminating > the need to mute the strings on the far side of > the bridge? After all, > mutes of any kind work through frictional > dissipation of vibrational energy. > Isn't it reasonable to expect that muting > adversely affects a note's > sustain? I suppose that depends on how you believe the rear duplex is put into vibration and what effect the vibration of the rear duplex has on the sound. If the rear duplex is being put into transverse motion by the up and down movement of the bridge (which itself is a subject of some disagreement on this list) which is being driven by the motion of the speaking length of the string, then this transverse movement of the rear duplex would occur anyway, whether it was muted or not. No additional energy is being sapped from the speaking length, so to speak, to 'drive' the transverse motion of the rear duplex. If this portion is muted it is simply dissipating the vibrational energy of the duplex, not the speaking length. This raises the question - is vibrational energy in the rear duplex a positive thing? Or the questions - does this improve the tone? Does this improve the sustain? I believe that this is one of the essential points of the discussion. > objectionable ringing in > nonspeaking string segments at inappropriate > frequencies, isn't an alternate > solution to tune those frequencies to where > they are appropriate and > therefore not objectionable? This is also one of the main points of the discussion. What do you call objectionable ringing? What is an inappropriate frequency? Certain people seem to think that the rear duplexes need to be 'tuned' and others think that this is not necessary. There doesn't seem to be any data (other than anecdotal evidence) to support an improvement in tone (which in itself would have to be defined) or an increase in sustain (which probably could have a definition that most of us would agree on) due to tuning duplexes. If you can do some experiments to provide some there are people on the list who have expressed interest. > > I am reminded of a closed field speaker system > I once designed for my > research... I > first attempted this by muffling > the ends of the tube in order to avoid > resonance peaks about every 120 Hz.... >Hopefully the parallels to > the duplex scale are obvious > here. Where possible, it seems best to correct > the tuning, rather than to > kill the sound. > > Peace, > Sarah > I'm not sure that the parallels are obvious to me. In the system you describe it seems that the various resonances are actually sapping energy that is being input. Muting them would cause even more energy to be dissipated. As I described above, I don't think that that is the case with a duplex. Experiment may show otherwise. I look forward to the data that shows me to be wrong. Phil F
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