Elie Riachi
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Parabolic reflectors
| Quote: | Originally posted by Dr. Oud
OK, I understand how parabolas focus electromagnetic waves, but my understanding of sound waves is that they act on the air (or water) molecules to
create vibrations that propogate rather than eletromagnetic waves that act more like projected or uni-directional waveforms. My point is that even if
you stand behind a speaker, you will hear the sound (although muted) but if you stand behind a flashlight, you're still in the dark. no?
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I have taken the liberty of moving this discussion out of Jameel's Next next oud.
Hello Doc,
Based on my understanding of the physical principals, if you aim the flashlight at an efficient reflector enough light will get reflected to
illuminate the are behind the flashlight. Also if you can see the objects which you are aiming the flashlight at as you stand behind the flashlight,
then you are seeing the light reflected from the object so you are not really in the dark.
One of the ways we hear the sound as we stand behind the speaker is by reflection of the sound waves by objects in its path. This happens as the
molecules of the medium, in this case air compression and rarefaction occurs (Hi and low pressure) so the disturbance created by the sound source
moves these molecules back and forth in a pattern which match the source (note the individual molecules do not travel a long distance but oscillate
about their equilibrium position like a block suspended from the end of a spring.) The molecules oscillating near objects may collide with these
objects, and depending on the properties of such objects, portions of the molecules' energies get absorbed and the rest gets refracted and or
reflected.
As far as the oud's bowel goes, if the location of the source of vibration is place near the focal point of the parabola then the waves are reflected
close to being plane waves. Anyway, I am not sure if a noticeable difference exists as a result of these reflection conditions. The biggest effect
might be coming from the change in the volume of the bowel or the effective depth of the air column both of which I think work in conjunction with the
size of the sound hole!
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Brian Prunka
Oud Junkie
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I would add that with a speaker, the speaker is moving in two directions, creating sound waves both in front of and behind it. If the speaker is in
sealed enclosure, this is minimized, but I imagine some sound is still transmitted through the materials of the enclosure.
I have noticed that some ouds transmit nearly all the sound forward (to the point where it's difficult to hear oneself play if there's not a nearby
reflecting surface), while others create a much more diffuse sound area.
Incidentally i recently was near a metal dish big enough to stand in; when speaking while standing in it, it focused all the sound at another
point--very weird to experience.
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Jameel
Oud Junkie
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Interesting Brian. There's a spot in my office where I practice that reflects so well that it's almost like turning on an amplification system. It's
really quite a great way to hear oneself, and the sound of their oud. (But frankly, nothing gives me greater pleasure oud-wise than hearing a pro play
one of my ouds!!--it's much more satisfying than playing alone.)
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Elie Riachi
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Has anyone tried singing in the shower? The voice sounds stronger because it is getting reflected back from all directions so it gets intensified.
Hummm, tried playing oud in the shower, anyone?
PS: shower walls are plane reflectors and not parabolic.
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Dr. Oud
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| Quote: | Originally posted by Elie Riachi
Has anyone tried singing in the shower? The voice sounds stronger because it is getting reflected back from all directions so it gets intensified.
Hummm, tried playing oud in the shower, anyone?
PS: shower walls are plane reflectors and not parabolic. |
Here's a carbon fiber one piece oud that would play in the shower I bet. I have played in the shower myself - without the water on, of course.
Regarding my flashlight analogy, I understand if I shine into a mirror I am illiminated, but if an object is illuminated, I'm still in the dark,
aren't I?
I get the moleculer excitation characteristics of sound waves, but aren't electromagnetic waves actually propogating through the air rather than
exciting molecules? Please educate me on this, Dr. Elie.
As for oud bowels - I have heard some rather small ouds with hemispherical cross section that are very loud and deep sounding - Manols, some
Karibyans, and that Hamza Usta for example. I think the factors are more complex than the size and/or shape of the bowel...but we are compelled to
emulate the old master's design in hopes of discovering what makes them sound so good. My theory is that they were well made so they lasted and they
got old. Nothing improves an oud like age - that's why aged tonewood is so expensive and rare. What we really need is a time machine so we can make an
oud 50 years ago. Do you have a design, professor?, hmmmm?
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oudplayer
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hey all
I was thinking and could you put the back of like a ovation guitar back on the oud
i thikn thats what the pic is above but maybe not
thx sammy
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paulO
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Hi All,
1. Make it a tile shower, it sounds great !! What reverb !!
2. As far as ovation style oud backs -- I remember somebody yaking about using this idea to make lower cost ouds -- might have been the Mid East Mfg.
guy....forgot his name. This must have been like 15 to 20 years ago. I never did see one though.
Cheers,
paulO
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Elie Riachi
Oud Junkie
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Dr. Oud,
If you see the object when you aim the flash light at it then some of the light is getting reflected (in some cases part of it may get absorbed and
then remitted.) If you see the object then light has reached you, would you still consider yourself in the dark?
As for a time machine to age wood check these links out:
http://www.wnmc.org/articlelive_php//blogs/46/Cremona&%2339%3Bs...
http://www.npr.org/templates/story/story.php?storyId=1972690
http://www.kulviolins.com/
There is also a biophysicist or a biochemist who has done some very extensive research on processing the wood the same way believed wood was processed
from cutting to transport down the river to milling during Stradivari times in hopes of producing a Stradivarius. This research included
experimenting with different chemicals to age the wood as well as different recipes of varnish. There was a very interesting Nova show on this
scientist's work a few years ago. In a sense he has been the closest to building the time machine. If I find a better link to his research I'll post
it.
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Dr. Oud
Oud Junkie
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Location: Sacramento, CA, USA
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| Quote: | Originally posted by Elie Riachi
Dr. Oud,
If you see the object when you aim the flash light at it then some of the light is getting reflected (in some cases part of it may get absorbed and
then remitted.) If you see the object then light has reached you, would you still consider yourself in the dark?... |
I guess you got me there, I hadn't considered the optics approach. But what if the object is a ninja dressed in black, in a black
room, will he see you behind the flashlight? I think that's why you see cops holding their flashlights above their shoulder, so if they're shot at
they won't get hit in the vitals, hopefully.
Very cool violin links btw, although the violin compared to an oud is like comparing apples and puppies, I think. You'll notice they talk about their
discoveries only in general terms. Nobody's gonna give up their instrument secrets for free, you know, and some never do. The aged and treated wood
phenom is interesting, though. I looked into the Lake Superior wood thing (logs salvaged from virgin cut lumber lost in lake Superior over 100 years
age). The wood is unique and very dense, but I heard the guitars and violins made with it didn't sound very good. Miles Gilmer (of Gimler Import
woods) thinks they soaked too long and the cellular walls got soggy, losing the structure to transmit vibration. I heard that Stradivari made his
soundboards from old spruce oars, so they were pretty leached out when he got them. But then that's violins, and a lot of the tone is due to the
varnish, I believe. In the end, I think it's the playing for those many years that contributes a lot to the sound, not just the aged wood to start
with.
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Elie Riachi
Oud Junkie
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Registered: 4-9-2004
Location: Kansas
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Mood: Gebran Tueni Lives For Ever, 12-12-05.
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Hi Doc,
The ninja will not see me behind the flashlight if there is nothing in the room to reflect the light except myself and the flashlight, and no light
from the bulb leaks behind the flashlight (assuming the ninja's uniform and face paint and everything else in the room including walls absorb light
enough that what gets reflected is low enough intensity that it is undetected by the unaided human eye.) I will not even see the ninja.
Sounds like Gilmer has a good point.
There is a theory regarding the period that good stringed instruments were made which ties the cold climate during the growth period of the wood used.
Interesting to listen to this theory here:
http://www.npr.org/templates/story/story.php?storyId=1544179
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Dr. Oud
Oud Junkie
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Registered: 12-18-2002
Location: Sacramento, CA, USA
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Oh great, now I have to wait to be reincarnated during another ice age to get those slow growth trees. Oh Man!
btw, I think you would see the Ninja's eyes, just before he got you with a poison dart or something.
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Dr. Oud
Oud Junkie
Posts: 1370
Registered: 12-18-2002
Location: Sacramento, CA, USA
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Mood: better than before
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| Quote: | Originally posted by oudplayer
hey all
I was thinking and could you put the back of like a ovation guitar back on the oud
i thikn thats what the pic is above but maybe not
thx sammy |
This is actually a carbon fiber molded oud based on a 3d cad model. It was produced secretly at
government expense, and would cost about $30,000. I guess that makes it a stealth oud.
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