Re: [Harp-L] SPAH 2010 Comb Test: a thought experiment (long)

["Rick Dempster" <rick.dempster@xxxxxxxxxxx>]

I admire Vern's patience over all these years. I always say to myself that I won't chime in on this again, because I'll just be repeating what's already in the archives.
What the hell! Here goes one of my favourite examples again: 
Observing that the inside of a music box looked a little like a set of harmonica reeds, I always believed that it might be possible to amplify (non electronically) the sound of the harp.
Holding the mechanism of a music box in your hand, the volume is tiny. Place it on a solid wooden table, and, like a tuning fork, the volume is magnified many times and is perfectly audible.
Now get someone else to blow a harp held in their hands as usual, then have them place the back of the comb against the same solid wooden mass that so amplified the music box mechanism.
The difference? Nil, because of the lack of vibration transmitted from the reed to the comb.
(BTW the reason I say 'someone else' is so you can hear properly. If you squish yourself up against the table or whatever, the closeness to the sound reflections might cause you to think there is an increase in volume. From a few steps back, there is clearly none.)
With the music box reed, the tuning fork and the guitar string, you are hearing the bell-like resonance of the metal. With the harmonica/accordion reed, you are hearing the whirring noise of air being chopped up, like the sound of a fan or an aeroplane propellor (do the materials of a plastic/metal/wood  propellor/fan cause respective differences in sound? I think not.)
I wish to hell the pro-materials-makes-a-difference mob were right; I would love my harps to be as loud as a trumpet or sax with no electronics involved. I have mucked about with trying to attach a reed to a guitar-face and to an old clockwork gramaphone head (read 'resonator') but it don't work. 
Does anybody not wonder why the Dopyera Brothers or some other mob back in the 20s didn't try to amplify the harp with a resonator, like they did the guitar, mandolin, violin, ukulele and gawd knows what else? If there'd been a buck in it, they would've. They didn't, because you can't. Go on! have a go!
The whole thing is a no-brainer.
Your's empirically,
RD

>>> Vern <jevern@xxxxxxx> 3/09/2010 15:46 >>>

On Sep 2, 2010, at 7:34 PM, Michelle LeFree wrote:
> 
> ...............I fully realize that this idea is in conflict with Vern's long-standing position. His argument that the wavelength of the sound a harmonica produces are much longer than the dimensions of a reed chamber and therefore the comb material can have no effect on the transmitted sound seems to hold water.

My argument about the size of the chambers was to refute the notion that the air in the chambers could form a resonant cavity or column.  

> Yet, how can this clear difference in how harps vibrate in the player's hands and mouth ~not~ bear some sort of a relationship with the sound emitted out the back of the harp?

Only for the sake of argument, let us assume that the combs of different materials vibrate more or less.  Their exposed area thus acts as a loudspeaker.  However, the very small area of the exposed surfaces and the small amplitude of the vibration produce a weak sound that is masked by the far louder sound of the modulated airstream.  This is like starlight in the daytime.  We all know it is there but it is masked by sunlight.

If you tried to design a structure that would resist vibration, you could hardly do better than to laminate layers of material of different acoustic impedances, (air, wood, brass) then filligree them with a lacework of openings.  All of these boundaries cause internal reflections that bounce the sound back and forth between the interfaces to be absorbed without ever reaching the outside.

If this were a perceptible effect and part of the harmonica playing experience, some of the six players would have felt the differences...or lack thereof in the brass comb repeats.   

Vern