Re: [Harp-L] A few thoughts on reeds, since we are muzing it seems.

[Vern <jevern@xxxxxxx>]

On Aug 10, 2010, at 6:29 AM, Dr. Michael J. Marino, DC wrote:

> 
> 
> Since we already know that the frequency you get is a complex result
> (tip width, length of reed, elasticity of the metal, density of the
> metal)
I would like to add two and subtract one from your list of variables that affect pitch:
- Width does not directly affect pitch. Think of two reeds side by side and vibrating synchronously. Joining them together would produce a reed twice as wide but of the same pitch.
+ Thickness at the tip affects pitch because it affects the moving mass of the reed.
+ Thickness near the rivet affects stiffness or the restoring force on the moving mass at the tip.


> why not see if we can take it one set further and see if the
> complex curved free reeds used in concertinas and accordions can be
> applied to the smallest of the family the harmonica. Bear with me as
> this is not just being a stick in the mud. The complex edge curve you
> find in high quality concertinas and accordion instruments helps to
> eliminate unwanted secondary harmonics that are not naturals of the
> root frequency desired.

> Now if this was applied to the harmonica we could get a much truer
> and sweet note from the instrument as much of the noise would be
> eliminated.

Harmonicas have a characteristic sound.  Many players would not welcome changing that because the result might not sound like a harmonica.
> 
> Now comes the question of how to test and find if this makes a
> favorable sound or one that takes away from the qualities that area a
> harmonica. I am just beginning to look deeply into the math that goes
> with this and it can make you head spin. So anyone interested please
> contact me as the outcome could be very interesting indeed.

Theoretically, rounding the tip of the reed or slot (in the plane of vibration) should change the change of flow area with respect to time as the reed swings through the slot and should weaken the high frequency overtones.


> FFT Spectrum analysis software is available for your PC.  I suggest that you alter the reed/slot as you suggest and compare the before and after spectrograms.

You might also compare these spectrograms with the spectrogram of the same note on a concertina.  

Vern
> 
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