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

[Vern <jevern@xxxxxxx>]

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