Spring Line Hum

[Paul Perry]

At 07:49 AM 18/07/00 -0600, Ian Fritz wrote:

>Well, you could probably make that sorta work. My concerns are that (1) the
>extra mass will perturb the springs mechanical response, because it would
>take a torque to move the foil and the spring is *very* soft in torsion.

the mass of a suitable foil would be VERY tiny. And, it should be remembered
that 
any magnetic pickup is itself responsible for considerable drag on the 
vibrating string. (hence eg 'magnetic damping')

>(2) the foil will add a lot of damping because it has to move air out of the
>way. 

I cant see this. The foil is not moving ANY air at all, it is rotating.
Consider a disc rotating like a wheel on an axis. If thin, it rotates with 
practically no movement of air.
Now consider the disc with a slot in it (to pass a variable amount of light).
This, too, does not displace air appreciably. True, there will be some 
miniscule drag, but losses would I believe be less than in a magnetic pickup
situation.

perhaps someone with a steady hand and a home workshop will solve this
for us! An advantage of the disc shutter system, is that you could have more
than one 
shutter disc on the same spring & add the effects together (or more properly
'multiply' the effects) with possibly amusing results.

paul perry melbourne australia

BTW, it is common in experimental sound sculptures to make the resonances of a 
taut wire more 'interesting' by using two or more sections of wire with
different
thicknesses joined together.  (that is to say, using two guitar strings for 
example of different gauge tied together) Perhaps resonance springs should
be likewise?