[en] Tunneling spectra have been obtained for Pb/GaS/Pb an Pb/GaSe/Pb junctions at 1.8 K for the normal state of Pb in the external magnetic field as well as for the superconducting state. The insulating barrier of GaS or GaSe, whose thickness is several unit layers, is cleaved from a single crystal. The observed structures in d²V/dI² characteristics have been interpreted in terms of inelastic electron tunneling due to the coupling between electrons and phonons of the barrier. The main tunneling structures show quantitative agreement with the energies of phonons having the wave vectors near the edges of the Brillouin zone rather than its center with our sensitivity of measurement. The relative line intensity and its bias voltages of the d²V/dI² structures do not agree quantitatively with the density of states of phonons calculated previously. (orig.)