Re: plans/ schematic for a guitar/ instrument string sustaining device??

From: Kevin Aylward (salesEXTRACT_at_anasoft.co.uk)
Date: 10/27/04 

Date: Wed, 27 Oct 2004 13:23:32 GMT

Rich Grise wrote:
> On Mon, 25 Oct 2004 08:17:46 +0000, justin wrote:
>
>> In article <417b8e83$0$21752$afc38c87@news.optusnet.com.au>, Clifford
>> Heath <no@spam.please.net> wrote:
>>
>>> Kevin,
>>>
>>> Justin was responding to my (now apparently somewhat OT) message
>>> about how the LBLers do this "with a view to measuring the response
>>> characteristics of the strung instrument". So that turned out not
>>> to be what the OP wanted, and Justin returned to the original
>>> request. I guess that was fair enough, but in the process he
>>> discounted all I said on my topic, and I objected - because for the
>>> issue I addressed, it matters. Nuff said.
>>
>>
>> Sorry to cause a stir, I am not discounting what you're saying. It is
>> well known to me that string frequency will vary over the duration
>> of a note because of a nonlinear mechanics of a string. After all,
>> if it wasn't for that - a string would be unusable. But this side
>> effect anomaly is so subtle and irrelevant to a musician that it has
>> only a theoretical significance, probably only to hair splitting
>> nuts like us ;)
>>
>> This is the part I was responding to:
>>
>>> behavior of the string is surprisingly strongly affected by the
>>> mechanical impedance and frequency response of the guitar as a
>>> whole,
>>
>> This makes an either very badly formulated or simply _not true_
>> statement.

Yep. The statement is fundamentally wrong.

>>
>> About the "behavior" - disregarding the amplitude part because it is
>> dependent on an exitation, an external factor - and focusing on the
>> frequency: mechanical /acoustical properties of a guitar have NO
>> effect on a frequency - the pitch, not the tone - of a string.
>>
>> You can take the same string from acoustic guitar and put it on an
>> electric solid body, or strung it between two nails on a marble
>> floor - it will unconditionally resonate at an exact frequency, i.e.
>> it's behavior is not affected.
>>
>> Maybe a more precise way to say what you intended was to restrict
>> that to: the _tone_ (and tone only) of a string is affected by
>> physical characteristics of a guitar.
>>
>
> I'd submit that the frequency will be measurably different from an
> acoustic than from a string with the exact same bridge and nut, and
> exact same tension, mounted on a marble base, because the the top of
> the guitar will be part of the resonating mass.

And your submission would be wrong. The resonating mass has nothing to
do with the problem. Some of us have actually done this "vibrating
string" problem in formal courses. Sure, there are a few minor
subtleties, but as I already stated, the frequency of the string is
essentially determined by the mass per unit length and the tension. A
point on the string goes up and down with acceleration force =
dl.rho.d^2y/dx^2, the tension can be resolved into x and y planes
etc...all from memory...:-)

The obvious subtlety is that the tension changes a little as the string
moves, so this changes the frequency a little, but this is very minor.
If it were too drastic, guitars would sound out of tune when hit hard.
They don't.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
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