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发表于 2011-1-3 21:41:07
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海外工程師的回覆
This is my $.02 FWIW. The theory is...when a guitar is built, a certain "preload" is built into the guitar, just by virtue of the bending of the wood, and the glueing process. This leaves the brand new guitar stiff and "tight". This carefully kiln dried tonewood has not yet had any time as a resonator, or "vibrating natural amplifier", for the frequencies generated at the point of the bridge. As the strings transfer their energy thru the bridge, and then to the soundboard, the soundboard vibrates...a little. The "spaces' between the wood fibers are still very tight, because the wood has not had experience as a "vibrating sound amplifier". As you play the instrument over the years or...(according to the claims of this maker, use the gadget on the instrument), the more you vibrate the soundboard, and the more those repeated vibrations tend to push around or, compact, the fibers of the tonewood together, "opening up" the spaces in between the fibers, making the soundboard more pliant, increasing the amplitude of the soundboards movements, moving more air, increasing volume, "breathiness", and a certain percieved improvement in the tone of the instrument. If you have ever bent a piece of aluminum rod stock back and forth several times, you will see cracks open up where you have bent the aluminum. This process is called "work hardening" when it comes to aluminum, and is not the same process which happens to the tonewood, but visually, it demonstrates how flexing a material with an even, or consistent density, like aluminum, creates certain desirable inconsistencies of density, in the case of wood between the "rings" of the tree from which your soundboard was cut. Perhaps I should instead say, that the vibration process "enhances" the inherent inconsistencies of density between the annual growth rings in the wood used in your soundboard. It is those inconsistencies which cause a thin piece of softwood like let's say, spruce, to flex under load, more than the equivalent thickness of a hardwood like oak, which would flex more than the equivalent thickness of an even denser material like steel. Aging is a different qualitative agent involving oxidation, and other factors you could call entropy (also allowing the instrument to "relax" over time) which I believe works in synergy with the playing of an acoustic instrument to improve it's tone and volume. In other words, older instruments USUALLY sound better than new ones, within reason. Apologies for the tech speak, but, since you mentioned you are a scientist (I'm a retired engineer)...this also explains why the famous Stradivarius instruments are so valuable today. They have had centuries of playing and aging to open up! Also, as an aside, the chemical compositions of the varnishes he used, seemed to produce an unparalleled quality of tone, as the varnish worked into the woods he used, this composition over time seemed to actually change the molecular structure of the wood, and luthiers have been trying to duplicate his secret compositions ever since! Though long winded, I hopes this helps. I'm not a scientist, but I did stay at a Holiday Inn Express |
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