Timeline for Will a violin string keep vibrating for a longer time in vacuum than in air?
Current License: CC BY-SA 3.0
16 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 27, 2011 at 16:57 | comment | added | Georg | These inelastic components are nothing but "reality". Even a glass sphere or a steel ball are not perfectly elastic, on vibration/impact always a small amount of energy is dissipated. The reasons for that are as different as solids are different :=( Polycrystallinity or crystal imperfections often play a role. | |
| Oct 27, 2011 at 16:18 | comment | added | Ron Maimon | @George: What are these "inelastic components"? What is inelastic? There must be internal motion, and it must be either mechanical rubbing of large parts, or mechanical rubbing of microscopic parts. The rubbing of microscopic parts will not happen in a lattice, it requires irreversible conformational changes, which is entropy. I think you are not right. Also, it is no good to tell someone to "read up" on something--- just say what it is. Are you saying there are no polymer expansions in wood? That's not true. Are you saying they are reversible? Maybe, I don't think so. | |
| Oct 27, 2011 at 15:11 | comment | added | Georg | ""in wood, where there are polymer expansions "" I recommend You read on structure of woods. You will understand then, why violins are made from wood, not from rubber. Think of the sound of xylophones! | |
| Oct 27, 2011 at 14:52 | comment | added | Georg | When excluding air sound by vacuum, the nextmost important damping would arise from inelastic components of the wooden body, I guess. This is spruce (or similar) wood, rather light but rather soft as well. | |
| Oct 27, 2011 at 14:30 | comment | added | Ron Maimon | @Georg: This attenuation is possibly not negligible in vacuum, where there is no radiation of sound. This is one reason for the decay in minutes. What is the mechanism of damping in a violin in vacuum? It is the irreversible changes in the violin, as Vladimir says. This is the question. I believe the main mechanism is movement of defects in metal, but heat transfer in wood, where there are polymer expansions and compressions leading to temperature gradient. | |
| Oct 27, 2011 at 14:28 | history | edited | Ron Maimon | CC BY-SA 3.0 |
remove section
|
| Oct 27, 2011 at 9:30 | comment | added | Georg | This attanuation is negligible, sound is too fast compared to thermal flow. But nevertheless I voted down, because You rechurned. I recommend to read the entire thread before answering. The classical physics demonstration is a monochord on a solid block of hardwood, this shows the damping of all but sound transfer to body and air. | |
| Oct 27, 2011 at 5:16 | history | edited | Ron Maimon | CC BY-SA 3.0 |
add a little more
|
| Oct 27, 2011 at 5:13 | history | rollback | Ron Maimon |
Rollback to Revision 2
|
|
| Oct 27, 2011 at 5:12 | comment | added | Ron Maimon | @Zassounotsukushi: I didn't miss it---it is the entropic part of the restoring force that determines the temperature gradients in the sound wave, I just had a mental lapse. | |
| Oct 27, 2011 at 4:14 | history | edited | Ron Maimon | CC BY-SA 3.0 |
remove nonsense
|
| Oct 27, 2011 at 4:12 | comment | added | Ron Maimon | @Zassounotsukushi: Of course, I missed what is probably the dominant decay method for sound waves--- the flow of heat from hotter to colder regions in the adiabatic compression. This type of damping is different in wood and in metal because of the different thermal conductivities, but metal is a better heat conductor, and so would have quicker attenuation. I will have to reconsider this answer. | |
| Oct 27, 2011 at 2:13 | history | edited | Ron Maimon | CC BY-SA 3.0 |
added 1127 characters in body
|
| Oct 27, 2011 at 2:04 | comment | added | Ron Maimon | @Zassounotsukushi: I am sure you are right. My thinking was as follows: to generate heat, you either need internal slippage of domain walls or polymer junctions, or rubbing of parts, like a violin string against the bridge. The rubbing effects are at nodes, so they are asymptotically negligible-- the loss goes to zero with the amplitude, and I will ignore this. For a metal body guitar violin/guitar with metal strings, there will be no internal slippage, and the answer is correct. For wood and catgut, the answer is probably different. I will modify the answer to reflect this. | |
| Oct 27, 2011 at 0:03 | comment | added | Alan Rominger | While I think what you say is most likely true, I can't construe have any good arguments to justify it. We know there is significant energy dissipated in air because we can hear it, but we don't have a good basis to say the thermal energy is considerably less, or less at all. I think it is less, I just can't show it. | |
| Oct 26, 2011 at 22:08 | history | answered | Ron Maimon | CC BY-SA 3.0 |