This chart plots the sound radiation coefficient for a variety of frequently used guitar woods.  The bars are the means (averages) of the measurements of many different samples and the lines are plus and minus one standard deviation. The degree of variation is somewhat smaller than would be found in a random sample, as these pieces of wood went through a rigorous selection process before they ever got into my workshop.  The sound radiation coefficient can be regarded as an index of the amplitude of vibration that a material will sustain for a given excitation force (a dynamic property) combined with a measure of its stiffness for a given mass (a static property).  High values are generally what one seeks in wood used for guitar tops and backs.  Details on how these measurements were taken and how they are used can be found in the book. 

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