MOTM

Hi Elhardt,

Very interesting.  I'm thinking there are basically two possibilities here:

1) Use a voltage-to-movement transducer to induce vibration in the strings,
causing the instrument to "play" itself.  Of course, without fretting, the
instrument would be somewhat limited to the fundamental frequencies and
associated harmonics of the four strings (along with body resonances.)  You
could string the violin with steel strings and use electro-magnets to induce
movement.  Another option could be to use one or more piezo-transducers
mounted to the bridge.  If you are thinking of amplifying the resultant
signal, you could mount a microphone or piezo-pickup on the bridge and pass
the signal thru a pre-amp back to the synth.  Pickup location will be very
sensitive, I'm sure.

2) Use the violin body as a resonating filter of sorts; to pass an audio
signal "through" the body of the violin and recover the resultant signal.  A
voltage-to-movement transducer could be used at audio frequencies to
"excite" the body resonances, and a movement-to-voltage transducer could
then pick up the resultant signal.  Probably the optimal inducer would be a
very small full-range speaker mounted inside (!) the body.  The best pickup
would probably be a mic.  Another idea, you could mount a metal plate to the
bridge and use an electro-magnet to set the bridge into motion (but how
would you mount this? hmm).  Obviously, mounting locations would have the
greatest effect on the response of this filter; there are so many different
resonance components.

There are quite a few challenging issues here: obtaining the appropriate
signal levels for both inducing and recovery, transducer types, mounting
hardware and location, etc.  Sounds like fun!  I would be very curious to
hear how this experiment turns out.  FYI, I have dabbled somewhat with
piezo-transducer pickups on a cello, passing the resultant signal thru my
MOTM rig.

Cheers,
George

----- Original Message -----
From: <elhardt@...>
To: <motm@yahoogroups.com>
Sent: Sunday, November 03, 2002 1:58 AM
Subject: [motm] transducers, input or output?


> I've always thought that transducers were another name for pickups, and
doing
> an internet search that seems to be what they are. They convert an
acoustic
> vibration into an electrical signal. But when reading about the old Ondes
> Martenot keyboard instrument, they say that one of the speakers (or
diffusers)
> uses a transducer to drive the strings on one of these diffusers. Is there
a
> device that I can use that takes an electronic signal and converts it into
an
> acoustic vibration for setting a string in motion or driving the bridge of
an
> acoustic instrument? Something other than a speaker that is. I'm still
thinking
> about setting a violin in motion using a synthesizer.
>
> -Elhardt