Yow-yow-yowing bass strings

[Nathan Bower]

Hmm how about this:

As the string is struck, it moves upward in a bow, and because it is no
longer in a straight line is stretched, the tention across the string goes
up, and the tuning of the string changes.

I think that a strings modes would all be harmonic / in tune. However
loudspeakers can suffer from inharmonic distortion when the sound wave
travels from the center of the cone (voice coil) to the edge (surround) and
instead of being terminated properly, bounce back and intefere with the
original wave. They use FFT (dont know what that means) to make pictures of
speakers to determine how much inharmonic distortion is present. The same
thing happens with electrical impulses in network cables, and scsi cables
(hence scsi terminators).

I find it unlikely that either end of the string is "rebounding" any large
amount of energy.

N


----- Original Message -----
From: BobDavis88@aol.com
To: pianotech@ptg.org
Sent: Friday, January 24, 2003 7:58 AM
Subject: Re: Yow-yow-yowing bass strings


Thanks to those who have responded so far about this. I thought I'd better
send an interim response, so you'd know I'm still listening.

First, let me clarify what I know so far, and rule out a few things. I agree
with Ron that this is definitely not a voicing issue, nor a termination
issue. It's not in the leveling. It's not a leaky damper, nor an undamped
segment of another string. It's not in the hammer at all, or rather in the
angle of attack of the hammer (sorry Sarah, interesting post), since the
strings exhibit at least similar behavior when plucked; at least the yowing
ones still yow, and the clean ones are still clean. It seems to be in the
string itself, and consists of beats. What I really want to know is what is
beating against what, and while I really really really didn't want to
speculate, the hypothesis that seems most convincing to me so far was posted
by John Musselwhite:

"Would those problematic single bass strings have LMFs [longitudinal mode
frequencies] that are either unstable or out of tune with the rest of the
string?"

I have the CD from the Five Lectures, but I can't lay my hands on it right
now. However, my memory is while the longitudinal modes produce different
pitches, they are clear pitches, and not beating (?) Still, beating suggests
non-harmonic stuff beating with harmonic stuff.
-----
Well, I took a look at Conklin's patent on longitudinal mode design, and now
I understand more than I wanted to. It looks as if the longitudinal mode can
be tuned by controlling the weight per unit length of the wire, including
core and loading, and falls roughly in the area four octaves+  above the
fundamental pitch of the string. I still don't know for sure if this can
beat with the partials produced by the normal flexural modes, but I don't
see why not, and if so, I don't understand how you could reliably make bass
strings ever, especially if they are so sensitive that the same string on
the same model can come out either wonderful or hideous.

One of you scientists out there set us straight. I'm getting interested in
this, and I don't have time to be interested.

Bob Davis