Sound waves(The behavior of soundboards)

[John Delacour]

At 6:40 PM -0600 1/22/02, Ron Nossaman wrote:
>  >The string is not taut.
>>
>>JD
>
>It says that where?

It says: "One end of a metallic wire is connected with the 
sound-board of a pianoforte, and the other taken through the 
partitions or floors into another part of the building"

It is most unlikely that it was taut in these circumstances and 
certainly not necessary for it to be taut.  However it would have 
needed, I think, to be *fairly* straight.

You can perform a similar experiment by drilling a 2mm hole in a 
grand piano bridge and planting a straightish length of 2mm copper 
wire, say 60 cm long, with one end ground flat firmly in the hole. 
Then take a tuning fork in one hand, hold the free end of the wire in 
the other and press the fork onto the ground end.  You will hear the 
sound amplified by the board.

You can next hold the free end in a pair of small pliers and apply 
the tuning fork sideways to the pliers, or pointing in any direction, 
and get the same effect.

If you next do the same with a *straightish* length of say No.16 
piano wire, the effect will be the same.  While the fork is still 
sounding and being amplified, you can then curve the wire into an arc 
and observe the effect as you curve it and straighten it.

In neither case does the wire need to be taut, and if you were to go 
to the trouble of drilling right through the board and knotting the 
wire underneath so that you could apply tension to the wire, it would 
make very little, if any, difference.

After all this, you can tell me how blindingly obvious it is that the 
fork moves the wire and the wire moves the bridge.

JD