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I didn't know a fork made a "Fandrich" sound when dropped!

B986,

Many thanks for your perspective. It made for interesting reading.

+1

I think I've just been insulted--but I'm not sure why...?

ddf

Now, this is indeed Gobbledegook! Give me a break!

No worries Del, the comment had nothing to do with you and I'm not sure why Opera Tenor made that connection. Dropped forks typically make a "png, ting,ding,tang,kang,pung" type of sound.

All the junk science, pseudoscience, and new age mysticism in support of the granite bridge bring my BS detectors to full alert. What's next in the world of pianos--pyramid power??? As it turns out, granite is not a very good conductor of sound--it is very lossy, which is one of the reasons it is used in high-precision machinery, where vibrations are a problem, and a material that damps them out is very desirable.

Hold a bar of steel or aluminum so they can vibrate freely, and when given a rap, they will ring nicely--think of a tuning fork. If you do the same with granite, it will simply produce a thunk. Actually, the density and modulus of granite are very close to that of aluminum. Granite is harder, but the only place in which hardness is of particular importance is at the string contact, and various bridge agraffes that use steel at the string interface have addressed this issue. Will the granite bridge sound different? Sure, it is heavier and stiffer than wood--so are lots of other materials. Yawn...

My first thought is that if this is desirable, which I doubt, concrete should work just as well, and it could be molded, rather than carved, which would be cheaper.

Do bridges conduct sound or simply cause soundboards to move with the strings?

Good point--one might argue that bridges are short enough (distance from string to soundboard) that all one really needs is a material with adequate stiffness and low enough loss.

My comment about granite being not such a good conductor of sound was made only because of the claims that were made by the inventor.

Quite so!

Granite tunes to the earth frequency, that is the fundamentals of that physics probably...

May be granite bridge will protect us against cancers caused by the Monsanto based corn that we eat every day, and that killed half of the rats that where eating them for 2 years ...

Lets go to esoteric talk ...

It is the function of the bridge to conduct energy from the vibrating strings to the soundboard.

ddf

Yes, but how?

When we were kids we used to attach two tin cans to the ends of a length of string and use them, with the string pulled tight, as a primitive telephone transmitter and receiver.

Later on we messed around with loudspeakers where the diaphragms move with the coils.

Coming back to pianos, Gabriel Weinreich showed how the oscillations of unisons couple through the bridge while you, Del, recently explained how the length of the backscale affects the movement of the bridge soundboard.

In essence, does the bridge conduct energy like that string, or does the soundboard and bridge assembly vibrate like a loudspeaker, or is something else at play, or a combination?

Speed of sound in wood across the grain is about 1/3-1/5 that of going with the grain. With the application of a wood bridge there will be some losses due to grain orientation we need to carve it. I believe this is where a material that has uniform sound transmission qualities in every direction would be more suitable than wood which has limitations in this respect.

(I’ve been following this topic with some interest. It’s been around before: https://www.pianoworld.com/forum/ubbthreads.php/ubb/showflat/Number/1419415/Searchpage/1/Main/101923/Words/Di+Santo/Search/true/Re:%20Stone%20Tone%20%28Granite%29%20piano.html#Post1419415
I wasn’t really planning on commenting on this topic but since I’ve kind of allowed myself to be drawn in….)

The soundboard functions something like a loudspeaker diaphragm. The energy source is the vibrating strings; their energy is coupled through the bridge to the soundboard panel. Look underneath your piano and observe the ends of the ribs; this is the soundboard’s analog to the loudspeakers cone surround. It’s not an exact analogy but it’s close.

Everything attached to the system affects how it vibrates. The string plane—due to its stiffness and the fact that it is usually set up to actually press down against the bridge—impedes its otherwise free motion. That is, the soundboard’s vibrating characteristics are different when the strings are not attached than they are after the strings are installed.

The mass of the bridge affects how the soundboard system vibrates; as does—though to a much lesser degree—its stiffness.

In this case—i.e., the granite bridge—the mass of the bridges is being increased and the termination efficiency of the speaking (vibrating) strings is being changed. The stiffness of the bridges is also being changed but various tests have shown that, beyond a certain point, this has relatively little to do with soundboard performance.

I’ll pass on the claim that “Utilizing the stored energy within the atoms of the crystalline matrix of the stone provides a faster response and even clear sound with minimal to no percussiveness.” I’ll also pass on the claims of “healing” attached to tuning the piano to a pitch of A=444 Hz. These claims have been made for ages with no scientific validation that I am aware of.

In all variations made to the traditional piano archetype the laws of physics must still prevail; adding mass to the soundboard system—in this case via the bridge—increases the mechanical impedance of the system. This alters the energy transfer rate from the strings to the soundboard assembly with the result that initial attack volume is reduced and the rate of decay is reduced which we translate into increased sustain.

Increasing the termination efficiency will also alter the energy mix that will be transferred from the strings to the soundboard assembly but the direct effect is a little less clear. A lot of testing would have to be done to determine just what is happening as a direct result of the change in termination efficiency. In theory a less lossy termination should transfer more high partial energy to the system but the more massive bridge is less able to respond so I don’t really know what the ultimate response would be. I’d want to reduce the number of variables and measure and compare.

Basically I agree with B’986: the same result can be obtained in other, probably less cumbersome, ways. (I’m not a stonemason so I really have no idea how many hours it takes to produce one of these bridges. It’s probably longer than the few minutes it takes to produce a traditional wood bridge, though.) While I generally encourage innovative people to explore their ideas and dreams I can say with reasonable certainty that this one will never reach large-scale, or even limited-scale, production. Given some development it might be producible on a custom, more-or-less one-off basis but the technologies necessary to cut and process stone to make piano bridges are not going to make it to the factory floor. My recommendation for a market would be to fit these bridges to custom-remanufactured or instruments and market the difference. In the end I suspect it will achieve about the same level of market penetration as have the pianos utilizing glass soundboards.

ddf

Just a bad joke to get your attention...

Mariosa said some interesting thing in that regard : he can "hear/feel" the speed of tone going thru the wood in the soundboard/bridge assembly./

I also have that sensation I even can imagine that when listening to a recording.

I suggest that we need some damping at the bridge level so the energy is not reflected too fast. When we hear the whisles created by improper string mating it is a very short wave reflected from the hammer to the agrafe because the hammer cannot damp it.

I suspect a similar process may happen within the bridge himself adding that high pitched components in the tone attack that oblige the pianist to delay it with the sustain pedal, as i seem to notice on the video samples (I admit the more sonorous instrument, but I hear an use of the sustain pedal that is twice on the stone bridged piano than on the "normal" grand)

As often heard, "more is not always better, " etc...
The wire by itself is very certainly prone to produce a lot of parasitic tone in regard of its fixations and terminations, we dont have the musical use for, I often have noticed in "optimized' instruments how too much high pitched tones where present at any level of dynamics, and that, at last is not usual to my ears, nor I am sure it is advantageous.

The speed of sound through the bridge is of no particular interest or importance. The bridge is short, string to board. There is no appreciable time delay. Additionally, time delay does not correlate with loss. Materials and arrangements with large time delay can have low loss, and vice versa.

The bridge mostly needs to be stiff enough so that forces due to string motions can be transferred to the soundboard panel with little to no loss. Consider a traditional bridge in which the string bears both on steel pins and directly on the wooden surface of the bridge itself. The surface area of the string where it is in contact with the wood is very small. If there is any compression of the wood in the bridge it will occur right at the contact point. If adequate stiffness is of any concern, one need only use some time of bridge agraffe in which the string's forces are spread out over a larger area of the bridge.

To all who attended,

Special thanks goes out to Thomas Zoells for organizing our event, and to all the members of the PTG and others that attended our presentation @ the Pianoforte Chicago.

Thank you for your interest in Stonetone®. We look forward to meeting you all again on this exciting journey.