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

[David Pearce via Harp-L]

Will a cupping back on a chromatic harmonica that blocks holes 1 & 2 reduce the volume of those notes and change their volume or tone?
Conclusion: There is no discernible difference of volume or tone in the comparison of a harmonica with a cupping back on and one with no cupping back. A cupping back can be used to make hand cupping a chromatic harmonica easier due to its smaller size without negatively impacting the sound or volume of the instrument. I came up with this idea when I read about Vern Smith's experiment where he covered up 50 percent of the back of the harmonica and was not able to measure any difference in volume with an audio meter. Thinking about the science behind a harmonica practice and testing it to determine its efficacy will help to advance the instrument make more productive use of precious time.

https://www.youtube.com/watch?v=5JBAp6xPYHY

Keep on harpin!
David Pearce

[Vern]

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

[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.

[Joseph Leone]

I have a question. Who started the idea of: ‘as much harp in the mouth as possible’. Any takers?
sm0joe