Re: Waves

[John Denker <jsd@MONMOUTH.COM>]

At 09:16 AM 7/3/00 -0400, David Abineri wrote:
> Am I correct in explaining string instruments, to say that a string
> actually vibrates in many modes simultaneously when bowed or plucked?
> That is, is it producing its fundamental along with several harmonics
> all at the same time?

Sure.  The fundamental alone would be musically useless.

> Is it possible to show this behavior (if the notion is correct) with a
> string vibrator or other equipment, rather than just postulating to
> students that this does in fact occur?

The vibrator is unhelpful for this purpose.

Set up a reasonably long string, or preferably rope.  I just tried it with
10 meters of 3/16" dacron yacht braid;  very nice rope, heavier than string
but very, very flexible.

Rig the rope across the room.  A foot or two from one end, give it a sharp
whack with your finger.  Any student can see the resulting pulse.  (From
across the room, vertical polarization is easier to see than
horizontal.)  The pulse is quite localized, very small compared to the
length of the rope.  It keeps its shape as it runs down the rope, reflects,
and makes 10 or so round trips as it gradually decays.

This is obviously a direct visualization of a pizzicato string;  the story
for a bowed string is essentially the same but this is less obvious.

Does that answer the question?  If not, I'm confused;  please rephrase the
question.