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| Tap tone and grain orientation http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=24678 |
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| Author: | Sondre [ Thu Nov 19, 2009 6:39 pm ] |
| Post subject: | Tap tone and grain orientation |
Have any of you noticed a correlation between grain orientation and quality of the tap tone of woods? For example on quarter sawn vs flat sawn backs... Thanks |
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| Author: | the Padma [ Thu Nov 19, 2009 6:57 pm ] |
| Post subject: | Re: Tap tone and grain orientation |
No. Why, should there be? Quartered wood makes for a stiffer top...that about it. Flat, quartered or rift cut...like size...makes no matter. blessings the Padma |
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| Author: | Sondre [ Thu Nov 19, 2009 8:00 pm ] |
| Post subject: | Re: Tap tone and grain orientation |
Quote: No. Why, should there be? Don't know, so I figured I'd ask  For example, if rift sawn wood is less stiff, I'm thinking it would tend to have a lower pitch when tapped. So maybe it would have an effect on how long it rings too...? Thanks Sondre |
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| Author: | Alan Carruth [ Fri Nov 20, 2009 4:09 pm ] |
| Post subject: | Re: Tap tone and grain orientation |
Internal damping usually dissipates a fixed percentage of the energy in the wood per cycle of vibration. Thus the sound dies out after a certain number of cycles. At low frequencies, with fewer cycles per second, the sound can go on longer. By the same token, high damping 'eats' high frequencies, which is the thing you generally notice on instruments made with high-damping wood, all else equal. The damping factor of wood is another one of those things that tends to vary widely, even within a species. I don't have enough data to be able to say whether one cut or another tends to have higher damping in general. I did note that the 'perfectly skew' piece of Sitka I tested the other day had fairly high damping in the cross grain direction, but that need not suggest that all skew cut wood does. The resonant modes that produce the tap tones involve bending in both directions. As Mark Blanchard has pointed out, wood with higher than usual cross grain stiffness tends to work out better on wider patterns, like Jumbos, while wood that has a lower cross grain stiffness might have 'better' tap tones on a 00, or something like that. With high cross grain stiffness, the wave traveling across the plate can cover more distance in the amount of time it takes the wave to travel along the length of the top. Since the resonant modes are 'standing wave patterns' the stiffness ratio effects the mode shapes, and the quality of the tap tones. |
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