piano/violin

[Ron Nossaman]

>     Of course it should resonate! (vibrate sympathetically with the source
>of sound, i.e. the vibrating string.  How else does it transfer its
>vibrations to the air?  

The soundboard is a diaphragm, as you said, driven by the strings. It
ideally should respond fairly uniformly to a wide range of vibrational
frequencies without reinforcing or damping any particular frequency range
with it's own characteristic resonant frequency. The ribs are shorter and
the board is stiffer in the treble for higher frequency responses than in
the bass, where the ribs are long and the assembly is much more flexible.
The resonant frequencies of the soundboard change from one end of the
bridge to the other, as can be demonstrated by tapping on the bridge of a
de strung piano in various places. The idea is that the whole assembly
shouldn't resonate at any given pitch, like a window pane when flight 714
passes overhead on the way to Fairbanks. If it did, you could stand on the
damper pedal, play any note, and after a few seconds you would hear that
resonant frequency creeping in.

 
Ron N