[CAUT] More on Single String Beats

[Willem Blees]

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
> 
> 
> 
> 
> 
>