RE: [Harp-L] How does bending actually work? (the physics)

["Tom Klingl" <tom.klingl@xxxxxxxxxx>]

Klaus Rohwer is a physiscyst and he gives a very detailed scientific
explanation
http://www.klausrohwer.de/privat/hobbies/muha/muhapubl/muhaphys.htm. He also
uses a numerical model with a finite elements software to show what is
(theoretically) happening to a reed. The videoclips are quite impressing
http://www.klausrohwer.de/privat/hobbies/muha/muhapubl/moden.htm. He also
was able to film the process real-time
http://www.klausrohwer.de/privat/hobbies/muha/muhapubl/strobo.htm 

However you have to be able to read German to get full coverage. Dave Payne
might get a kick out of it...

Tom 

-----Original Message-----
From: Arthur Jennings [mailto:timeistight@xxxxxxxxx] 
Sent: Friday, March 19, 2010 7:11 PM
To: michael rubin
Cc: harp-l
Subject: Re: [Harp-L] How does bending actually work? (the physics)


I am not a physicist, but here's what I think is happening:

There are three resonances interacting in an unvalved bend: the draw reed,
the blow reed and your mouth. As you lower the resonant frequency of your
mouth cavity, you force the draw reed to vibrate at a lower rate. (This is
what is happening on a single-reed bend on a valved harp.) As the pitch gets
lower, it gets closer to the resonant frequency of the blow reed, which
excites the reed and causes it to vibrate.

You can observe this sympathetic vibration effect on a string instrument. If
you play an 'A' or the low 'E' string of a guitar and watch closely, you can
see the open 'A' string vibrate along with it. In fact, if you stop the note
on the sixth string you'll continue to hear it from the still vibrating
fifth.

On Fri, Mar 19, 2010 at 10:02 AM, michael rubin <
michaelrubinharmonica@xxxxxxxxx> wrote:

> I have often explained to my students that when draw bending, what we 
> think of as the blow reed takes over the vibration and does the bend 
> sound.  I take the cover plates off of a harp, I bend, I put my finger 
> on the draw reed, stopping the reed's vibration and the bend continues 
> to sound with vibration on the blow reed's part while the draw reed 
> has stopped.  This has satisifed many students, but today I have met 
> my match.
>
> How does the blow reed take over?  How does bending fool the blow reed 
> into vibrating quicker and producing a higher pitch?  What does the 
> symathetic vibration of the draw reed have to do with it? Thanks,
> Michael Rubin
> Michaelrubinharmonica.com
>



-- 
Arthur Jennings
http://www.timeistight.com