try again,

[Newton Hunt]

This is a very important concept, transducing vs amplification.  The
better the coupling of the string to the board the more efficient the
system will be, the more sustain and the more power.

The efficiency of converting finger motion to sound is about 5%.  The
amount of energy put out by the board is about 5 watts.

Yet, it is astounding how much sound a gifted pianist can get out of a
piano.

                Newton