  Acoustic wave front conjugation is studied in a sandy marine sediment that
contains air bubbles in its fluid fraction. The considered phase conjugation is
a four-wave nonlinear parametric sound interaction process caused by nonlinear
bubble oscillations which are known to be dominant in acoustic nonlinear
interactions in three-phase marine sediments. Two various mechanisms of phase
conjugation are studied. One of them is based on the stimulated Raman-type
sound scattering on resonance bubble oscillations. The second one is associated
with sound interactions with bubble oscillations which frequencies are far from
resonance bubble frequencies. Nonlinear equations to solve the wave-front
conjugation problem are derived, expressions for acoustic wave amplitudes with
a reversed wave front are obtained and compared for various frequencies of the
excited bubble oscillations.
