Think about this: a process for converting sound into x-rays but not involving hydrogen or sonoluminescence….
The conference papers from ICCM/20-Sendai includes an important but overlooked paper “Developing Phonon–Nuclear Coupling Experiments with Vibrating Plates and Radiation Detectors” Florian Metzler, Peter Hagelstein and Siyuan Lu This was available on the LENR-CANR site but for some reason a proper URL citation cannot be found. Also, apparently it has been updated with further work recently. Abstract Excess heat has been reported in cold fusion experiments since 1989; however, there is at present no accepted explanation for what mechanisms are involved. Over the past decades a general theory has been developed which seems applicable to excess heat and other anomalies systematically; but in this case we do not yet have unambiguous experimental support for the phonon–nuclear coupling and enhanced up-conversion and down-conversion mechanism. This has motivated experimental studies with which we hope to develop relevant experimental results from which clear tests of theory can be made. A facility has been developed with which we are able to induce vibrations in metal plates from about 10 kHz up to about 10 MHz and then measure the relative displacement. With a high-power piezo transducer we have driven a steel plate at 2.23 MHz to produce a vibrational power of 100W We are able to detect X-rays… END. In short they put in sound waves which produce x-rays by upconversion. This seems to be related to the Mossbauer effect. No indication is provided of the power ratio in vs out but anytime upconversion is claimed, there is a potential avenue for gain unless there is a corresponding downconversion to balance the books. One variation which I would like to see is to irradiate iron (57Fe) with both ultrasound and RF at the first sideband absorption line at 34 MHz The is a surprising history in alternative energy of anomalous energy coming from iron. With MIT/Hagelstein on the case, answers may be forthcoming.