Dave,
Speaking of the implications of "sound in a vacuum", or lack thereof - one possibility of interest which may have promise for gain (Maxwell's demon type of gain) involves the so called "singing bowl" phenomena. These bowls can produce sustained ringing for extended periods but are of course not gainful in themselves (despite the apparent rise in frequency). http://www.youtube.com/watch?v=9e6oA02wk94 A tuning fork could substitute in this concept - but imagine such a bowl in vacuum, as you suggest. Now - however - the intent of this virtual experiment is that the sustained vibrations are applied in the context of a cold cathode. So, also imagine that the bowl-in-a-vacuum has a coating of graphene (or other low work function electron emitter) and that the bowl vibrations are used to break up "space charge" which is a limiting factor for cold cathode emission. BTW here is the favored cold cathode material - a bed of CNT http://techlinkcenter.org/summaries/cold-cathode-low-emission-threshold-and- high-current-density Given that ballistic electrons have a minimum potential which may exceed the work required to emit them if the space charge can be bypassed - there is the possibility of converting mechanical vibrations to energy, and thereby extracting ambient heat from the emitter as gain, which also makes the emitter more conductive for a bit of positive feedback . . or not. From: David Roberson The thermal power exiting each square centimeter of surface area is well within reason when 10 micrometer material is used and should not cause a meltdown according to preliminary figures.
