Sound waves

[John Delacour]

At 3:47 PM -0600 12/7/01, Ron Nossaman wrote:



>>I have enough empirical understanding of impedance to get by with 
>>for the moment -- the calculation of it and its use as a scientific 
>>design factor can wait a little.
>>
>>JD
>
>If you are expecting to get a method of producing soundboard impedance
>numbers by calculation from me, I'll tell you right now that you will be
>disappointed. I don't have one.

No, I will be expecting, from someone, some more solid description of 
the principle of impedance with practical examples.  When I get Joe's 
DOS program I'll be able to make a few deductions, I hope, and 
extract some numbers out of it.

When the number of strings in a unison falls, we increase the tension 
of the unison, stiffen the wire etc. in order to get an inaudible 
transition, don't we?

And when the treble bar of an upright necessitates the cutting away 
of the bridge, we need to make up for this either behind the board or 
by splinting (rare) the bridge.

We cut large holes in bass bridges and cant the long bridge in the treble etc.

All these things have always been done empirically, and you suggest 
that you still do at least some of them empirically.  Now the word 
impedance has been bandied about quite a lot on the list and there 
are now outstanding questions from people about the Z formula for the 
calculation of acoustic impedance, but so far we've had nothing 
approaching a definition of it or any example of the application of 
the formula, not specifically to bass strings but in general, for the 
principle will apply throughout the acoustic system.

It will not be obvious to a layman that the cut-out in the upright 
bridge needs to be compensated for, but any piano man knows that it 
does and has an inkling why.  Our modern piano man, airily discarding 
the universally laughable attempts of the late 19th century, will of 
course be able to calculate precisely how to make that compensation, 
precisely how big to make the holes in the bass bridge etc.

Where is this man?

JD