[CAUT] More on Single String Beats

[Porritt, David]

Are you sure those are differences, or a lack of repeatability of your
readings?  You have to have very sophisticated (read expensive)
measuring equipment to get repeatable measurements < 0.001.

dp

David M. Porritt
dporritt at smu.edu
-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Willem Blees
Sent: Monday, April 16, 2007 10:44 AM
To: College and University Technicians
Subject: Re: [CAUT] More on Single String Beats

I'm sorry, but I wrote down the wrong numbers. Instead .02 - .001", it 
should have read .009 - .001". And those were educated guesses on 
where the line was on my micrometer. 

Wim

Quoting Willem Blees <wblees at bama.ua.edu>:

> Quoting David Skolnik <davidskolnik at optonline.net>:
> 
> > Wim -
> > By coincidence, I was experimenting with just such a false beat
> this
> > 
> > morning on a newly rebuilt Steinway L fro the '20's.  On note C#7,
> 
> > treble-most string had a beat of appoximately 6-7 bps.  There was
> no
> > 
> > change in adding mass (as screwdriver) to any other part of the 
> > system.  In fact even touching the bass of the bridge pin with 
> > varying amount of force and from different directions produced 
> > virtually no change.  What did accelerate the beat rate was moving
> 
> > the screwdriver up the pin towards the top.  The pin did not seem
> to
> > 
> > be loose.  It seems possible that some aspect of the pin sets up an
> 
> > internal resonance that could interact with the frequencies created
> 
> > by that string.  I'd love to try something like pulling the pin and
> 
> > changing the length, or take complete measurements of weight,
> length
> > 
> > and diameter, and then alter one at a time.  Well, I mean note the
> 
> > changes of weight and length.  What's interesting too, is that 
> > sometimes, a blade placed on top of pin of a vibrating string 
> > vibrates quite noticeably, and at other times, such as this, not.
> > 
> > As far as your theory, I'm not sure I see how that might work. 
> Care
> > 
> > to elaborate?
> > 
> > David Skolnik
> > Hastings on Hudson, NY
> 
> David
> 
> I don't know how it works, per se, since I am not an electrical 
> engineer nor a metalurgist, but I just took an inch by inch 
> measurement of a #14 wire for about a foot, and found a slight 
> variation in several spots of between .02 and .001. My therory is
> that 
> it is this slight imperfection that causes "false" beats. 
> 
> Wim  
> 
> > 
> > 
> > 
> > 
> > At 10:30 AM 4/14/2007, you wrote:
> > >There is one thing that Ric mentioned that gives me reason to
> > believe
> > >the reason there are "false" beats is because of the differences
> of
> > >the diameter in the string itself. He said "the addition of mass
> to
> > >the strings front bridge pin, or an area very close to same has
> an
> > >impact on the speed of the beat.... and at some optimal degree of
> > mass
> > >addition (or even > subtraction perhaps) the beat disappears."
> > >
> > >When strings are drawn to size, it goes through smaller and
> smaller
> > >holes. The strings are pulled by an electric motor. As with any
> > >electric device, the speed of the motor changes as the amount of
> > power
> > >fluctuates. The surges in power are effected by other electric
> > >appliance starting or stopping.
> > >
> > >My theory is that in the factory where string is made, there are
> > >lots of large electric motors that stop and start constantly. It
> > >doesn't take much to cause a small surge in any of the motors. As
> > the
> > >surge occurs, it slows down the speed in which the wire goes
> > through
> > >the hole. This, in turn, changes the diameter of the string. It
> > might
> > >be so small that it is undetectable, but it might be enough to
> > cause
> > >the string to change it's beating pattern.
> > >
> > >Am I way out of it, or is this a plausible cause of false bats?
> > >
> > >Wim
> > >Willem Blees, RPT
> > >Piano Tuner/Technician
> > >School of Music
> > >University of Alabama
> > >Tuscaloosa, AL USA
> > >205-348-1469
> > >
> > >
> > >
> > >Quoting RicB <ricb at pianostemmer.no>:
> > >
> > > > Hi Folks
> > > >
> > > > Several off list discussions with a few well known piano
> physics
> > > > profs
> > > > has recently confirmed a now long held suspicion that the idea
> > that
> > > > classic false beats or single string beats are caused by a
> loose
> > pin
> > > > is
> > > > just plain way too simplistic and very far from complete.  In
> > fact
> > > > loose
> > > > pins can only account for a contributing factor to the overall
> > larger
> > > >
> > > > and holistic bridgepin / bridge / and soundboard termination
> > area. As
> > > > a
> > > > consequence of this it should be expectable to find this kind
> of
> > > > falsness in all registers of the piano, contrary to present
> > popular
> > > > belief that these are confined to the mid upper range of the
> > piano.
> > > >
> > > > Closer examination of what the overtones of strings in all
> > registers
> > > > of
> > > > the pianos does indeed reveal exactly this.  I am finding
> single
> > > > string
> > > > beating in all registers and these are of the sort that
> respond
> > to
> > > > the
> > > > pressure of a screwdriver or similar tool to the side of the
> > pin.
> > > > They
> > > > are quieter and harder to discern the lower you get in the
> > scale,
> > > > probably because of the wealth of overtones and amplitudes of
> > these
> > > > that
> > > > are present, but they are indeed and no doubt about it very
> > present.
> > > >
> > > >  From A0 to C8 one can find this kind of single string beat
> > popularly
> > > >
> > > > called the false beat.
> > > >
> > > > One thing I find curious, tho I have not confirmed it yet...
> is
> > that
> > > >
> > > > these beats seem to occur in range of 1500 hz upwards.  At
> least
> > in
> > > > the
> > > > ones I've been able to identify in bass notes... they seem to
> > convey
> > > > a
> > > > sense of being overtones in this range.
> > > >
> > > > In all cases so far, the addition of mass to the strings front
> > bridge
> > > >
> > > > pin, or an area very close to same has an impact on the speed
> of
> > the
> > > >
> > > > beat.... and at some optimal degree of mass addition (or even
> > > > subtraction perhaps) the beat disappears.
> > > >
> > > > It has seemed to me for a long time that this whole area of
> > sound
> > > > problems needs quite a bit more close examination as to what
> > really
> > > > causes this single string beat.  And it also seems more and
> more
> > > > evident
> > > > to me that a cure, and one which bears with it other tone
> > enhancement
> > > >
> > > > factors, lies somewhere in an <<optimal mass at the
> > termination>>
> > > > perspective as opposed to the idea that the pin simply needs
> to
> > be
> > > > tight
> > > > enough.  Especially since loose pins can so often be absurdly
> > present
> > > >
> > > > with no noticeable resultant single string beat.
> > > >
> > > > Cheers
> > > > RicB
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > 
> > 
> 
> 
> Willem Blees, RPT
> Piano Tuner/Technician
> School of Music
> University of Alabama
> Tuscaloosa, AL USA
> 205-348-1469
> 


Willem Blees, RPT
Piano Tuner/Technician
School of Music
University of Alabama
Tuscaloosa, AL USA
205-348-1469