  We study the resonant excitation of sound modes from Josephson oscillations
in Bose-Einstein condensates. From the simulations for various setups using the
Gross-Pitaevskii mean-field equations and Josephson equations we observe
additional tunneling currents induced by resonant phonons. The proposed
experiment may be used for spectroscopy of phonons as well as other low-energy
collective excitations in Bose-Einstein condensates. We also argue that the
observed effect may mask the observation of Shapiro resonances if not carefully
controlled.
