danieletarab - 11-23-2014 at 05:40 PM
Hi there!
In the next months I'll probably order my first custom oud; so far I have been playing second hand ouds, ready ouds I found in workshops or standard
models, like the reduced price arabic from Master Turunz.
I know that it has to be arabic, tuned in C, 61 or 61,50 cm string's lenght, without rosettes (easier to put pickups or mics in).
My doubt is about holes.
I really love ouds with big single oval hole.
My questions is: how do number, shape and dimension of holes affect the sound? What's the difference in sound between an oud with a single hole, and
another one (exactly the same) with 3 holes?
For example, I really like the oud that DImitri Rapakousis built for Navid from "oud for guitarists" (it has 3 oval holes), but I am afraid that if I
order one with a single hole I am not going to get the same sound. In which way could it be different?
I hope I have been clear enough!
Thank you!
bulerias1981 - 11-23-2014 at 07:42 PM
Hi Daniel,
To be honest, not a big difference in sound at all.
jdowning - 11-24-2014 at 03:42 PM
It all depends upon what you mean by 'sound'.
http://www.mikeouds.com/messageboard/viewthread.php?tid=14874#pid10...
danieletarab - 11-25-2014 at 03:50 PM
Oh my God Jdowning!!! You're a genius 
But unfortunately I am not! I tried to
read your amazing essay but I can understand only half of it I know that it's
very difficult talking about "sound" in ordinary language, but what I need to know is: if I have 2 ouds which are exactly the same a part from the
number of soundholes (one with a single big one, the other with3 soundholes, like a mounir banshir model for example), will they sound different? in
which way? Anyway, congratulation for you reasearch!
jdowning - 11-26-2014 at 05:35 AM
The bowl of an oud is a resonator that emphasises a certain band of frequencies of the instrument - usually in the bass. The range of resonance
frequencies depends upon the air volume of the bowl and sound hole area and diameter (for single round sound holes). So for a given bowl volume the
air resonant frequency range may be altered by adjusting sound hole area and diameter - increasing sound hole diameter will increase the air resonance
frequency (higher pitch) and vice versa. The perceived response of an instrument in a given resonant air frequency range would make it sound different
compared to the same instrument designed and built to work with a different air frequency range.
The same physics apply to ouds with triple round sound holes except that the air resonance frequency range depends upon not only the relative area and
diameter of the sound holes but on their relative position to each other.
So if two ouds - one with a single round sound hole the other with three round sound holes were otherwise identical in every other physical respect -
including their air resonant frequency range - then, yes, they would sound the same in 'tone colour' and loudness. The likely hood of that occurring
in practice, however, would have to be left to the imagination.
Note that sound hole shape also determines the air resonance frequency range which for a given air volume of bowl would differ if the sound holes were
round, oval, f shaped like a violin or whatever.
danieletarab - 11-28-2014 at 08:19 AM
Thanks a lot Jdowning! THat was very useful! As far as I undersand, according to what you wrote in your post, rosettes would give more sustain or I
got it wrong?
jdowning - 11-28-2014 at 12:06 PM
My original trials in 2009 using a guitar with a perforated disc fitted into the sound hole to simulate a rosette showed an increase in sustain of
100% compared to that with the sound hole open. See here starting 9-7-2009 onwards
http://www.mikeouds.com/messageboard/viewthread.php?tid=8488&pa...
However, most recent tests using a steel 'water tank' resonance chamber fitted with an old lute rosette indicated the opposite - a reduction in
sustain to 60% of an open sound hole of the same diameter.
The steel acoustic chamber is much closer to being a Helmholtz resonator than a guitar where the flatter geometry (compared to the deeper tank) and
greater flexibility of the guitar walls does affect the measured resonance frequency. So at this point in time I am not sure if the rosette pattern
does influence the sustain one way or another.
To check this out will require tests using yet another resonance chamber (#3) of larger diameter and shallow depth - to better simulate oud, lute or
guitar geometry. I do have a suitable scrap steel water tank that I can convert for the trials (that I also need to run trials on triple sound hole
geometries).
So watch this space for future information but don't hold your breath as I currently have lots of other projects 'on the go'!