Personally I agree with what was said by Ilike2beanonymous:
I removed the fluff/nonsense about "resonance", which has little, if anything, to do with how a soundboard works. Resonance is a specific aspect of sound mechanics which has to do with the frequency of maximum amplitude of a system. What happens with a soundboard is actually much simpler: it has a larger surface area than a string alone, and therefore can move a larger volume of air, hence a higher volume of sound. +ILike2BeAnonymous 

The term "amplify" is definitely true when it comes to the soundboard. I'm currently studying to become a pianotechnician myself and I would be very interested to hear your professionel explanation for saying that the soundboard does not amplify anything... As far as I know the word amplify has been used for a lot of non-electrical things for a long time now so I don't really see your point there either.
Care to elaborate?