[Harp-L] The results of the "cupping back" challenge by David Pearce

[Greg Heumann]

> 

Outstanding response from Vern! Because… Physics! I would add one other bit of info to the discussion. As a rule, I’ve found harp players underestimate the amount of sound that comes out the FRONT of the harmonica. If you don’t believe it, try completely sealing the rear of your harp with a piece of masking tape.  Good cupping involves using hands and face, as well as an “as much harp in the mouth as possible” embouchure. I couldn’t come CLOSE to doing this on a chromatic, but the more you can do the better. On a diatonic, it makes the difference between underwhelming  “wah" effects and great big “WAH" ones.  This is true whether playing acoustic or amplified. 


/Greg

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> There are two acoustic effects that prevent shape changes from affecting the perceptible volume of a harmonica.
> 
> Diffraction says that sound emanates from openings of less than a wavelength in a spherical wavefront pretty much equal in all directions.  There is no dimension of a harmonica that approaches the wavelength of sounds in the instrument?s range.  Therefore,  the shapes of covers have no directional influence.
> 
> The response of the human ear is logarithmic.  The sound power must increase by about 100% or decrease by about 50% before you notice a difference.  There is a story that may or may not be true about the young engineer who promised to redesign the exit nozzle of a jet engine to reduce the sound power by 50%.  He succeeded but his boss couldn?t notice the improvement and fired him.
> 
> Try closing a door with sound on the other side.  You will notice that there isn?t much difference between the door barely cracked open and standing completely open. There is a big difference in completely closed and barely cracked open. 
> 
> In harmonicas, the biggest sound change occurs between completely closed and a barely open hand cup.  The change between barely and completely open is much less. 
> 
> Vern