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Old 02-14-2010, 11:59 AM
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rick-slo rick-slo is offline
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Quote:
Originally Posted by DupleMeter View Post
And all of this just seems like running in circles, because for any of what you say to be true would mean you are playing a guitar that is greater than 13 feet in width at some point along the soundboard - because there is no other method for the instrument to produce it's own low note without the use of room modes (a 82.4Hz wave is about 13.7 feet long, a large guitar may have a 17 inch lower bout - leaving a discrepancy of about 12.2 feet of vibrating material to produce that low E). The guitar is producing a very complex wave of overtones to make you believe you're getting that (much like an upright bass has no chance of every producing its lowest note of 41.2Hz, only its overtones).
Interesting.
You are saying that an acoustic guitar can not produce a frequency below its maximum body dimension in relation to wavelength. So given a guitar's maximum body dimension which is in the neighborhood of 19 to 20" vertically the lowest note it can produce is about 700 hz. Any perceived tones below that is just a blend of yet higher frequencies which are deceiving the ears. Phantom fundamentals do exist but it is not the explanation here. One has only to look at the graphs posted here to see it is not just some psychoacoustic trick of our ears but that these lower fundamentals are present and measureable.
My headphones will produce sounds down to 18 hz and my 10" speaker drivers down to 28.5 hz. It is much less about size than what the driving forces are. Also with a guitar it is not just the length of flat pieces of wood. We are talking about an enclosed resonant cavity and most of the sound volume being produced by the guitar acting as an air pump.
That said in a decent recording environment and where people are not walking around I do not think there is a lot of very low frequency mucking about although there is some and it does not hurt to filter that out.
On another note it was mentioned that the spectrum graphs I posted earlier were not showing the low frequency energy properly and I should look at a Fourier graph.
Here is a snapshot of the same tune and the preponderence of the energy is right where one would expect it to be.
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Also at same recording just a moment before I started to play the guitar.
This shows that the lower frequency energy that was present was due to the guitar itself and room reverberations of its sound.
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Last edited by rick-slo; 02-15-2010 at 09:19 AM.
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