Сообщение
Nirko » Ср ноя 16, 2005 10:36 pm
¬Blues harmonica. Reeds.
Sketches.
1. What is reed in diatonic harmonica ? It's a very common free reed
musical instrument. Arguably, the most widely played, but not very explored instrument one.
2. Some animation about the design of diatonic harmonica.
3. Pass some opened harmonicas.
4. The reed makes the sound, and reeds are the most important parts in harmonica.
5. What happens to the reed when we make a sound? Let's talk about
the physics of harmonica. The first and the most important thing:–
reed vibration does not ensure harmonica sound. When you
take of the cover and make the plucking you can hear only tiny ping
sound, but not the sound of harmonica. The sound of the harmonica is
provided by the action of the reed vibrating through it's slot and
chopping the air stream.
6. As we can see from the diagrams the reed is deforming in various
directions, just like the guitar string which is vibrating in endless
directions and waveforms to create one note (the effect is similar to
playing a chord – you play several notes and at the measurements you
get one frequency, associated with one note. The guitar string is
producing an endless number of notes to create one single note)
7. Comprising the mentioned above, to create a sound with such a complicated system we should choose corresponding material for reeds.
8. I've contacted some major factories and received information about
material of harmonica reeds. Most of them use brass for
reeds and reed plates.
9. Horner – the biggest factory producing harmonicas provided me with
information on the exact name of the material. It's KA2, an
alloy which is very similar to brass.
10. Brass –is an alloy of copper and zinc. Pure copper can't be used
for harmonica reeds, because it has not enough plasticity and it's
subjected to corrosion, what is very important in harmonica because of
high humidity of air, forthcoming from player's lungs.
11. Short topic about brass – brass is versatile manufacturing
material because of its hardness and workability. It is well known since prehistoric time, it was used a lot because of its gold-looking color and good manufacturing properties. Brass is used
in brass instruments (as we can see from the name of the instrument
group) because of it's good acoustical properties (trombone, trumpet
and tuba). There are different types of brass – alpha, alpha-beta
brass and beta brass. They are different in ratio of copper and zinc.
When the brass consist more than 50% of zinc it means that it's
very brittle, but when you have about 30% of zinc (alpha brasses) this
brasses are malleable (can be shaped or bent without breakings), can
be worked cold and can be used in pressing, forging, or similar
deforming.
16. Some factories use phosphor in alloys, for springs. I can
suggest, that phosphors and zinc work similar to small particles
between molecules in rubber, what makes its deformation elastic,
since brass has a polycrystalline structure. And some researches (which
are enclosed to my work ) show that the combination of about 21%
Zn, 70% of Cu% and about 9% of other components, such as phosphors is
good for harmonica reeds.
12. The first property is important, because the reed must have a
capability of lasting over a great number of cycles.
13. Since the profile of the reed is milled on a sheet about 0.35mm
(the human hair), the last property is extremely important in choosing
the material.
14. As I said, brass is not subjected to corrosion, what is really important.
17. From my own experience of repairing harmonicas I can say, that
cheep harmonicas (and less long-lasting) have more red in the color of
the reeds, by I can suggest that possibly it’s bronze which
contains more copper and have similar characteristics with brass, but
it's more brittle, what makes it not the best material for our purpose.
18. The cost of the material : it's a very important issue, since we
don't want to make really expensive instrument. Brass is
one of the cheapest and common alloys – that's one of the reasons of
choosing it for our purpose. Bronze is cheaper, that's why it's often
used in cheap toy-harmonicas. But cost of the reed material is not so
important, as the cost of the reed plate, because reed-plate needs above
than 10 times more material, than reeds. Choosing the
material of the reed plate according to its properties isn't so
important, but brass has good acoustical properties and cheap types
of brass are used for it.
- For a long time harmonicas were hand-made, but progress came to this industry, and now instruments are made almost without any human intervention. But still best harmonicas are hand-made, and this affects to the choose of material too, to make manufacturing more easy.
19. At the end I should say, that my theme is pretty particularized,
and not well discovered yet, because harmonica is very young instrument,
but the harmonica community is growing from year to year and new
techniques are invented and harmonica became an instrument, not a toy
from the toy store.
