Oscillating Superleak Transducer of Second Sound

The superleak sound transducer is investigated theoretically. It is concluded that first sound is virtually never excited and that the characteristically low driving efficiency of second sound is caused by diffusion across the pores. Suggestions are provided on how to enhance the driving efficiency by several orders of magnitude. In ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A_1$, the signal strength is related to the magnetic properties of the diaphragm surface, opening new areas of application.