We report on parametric amplification in dynamic radiation force produced by
a bichromatic acoustic beam in a fluid. To explain this effect we develop a
theory taking into account the nonlinearity of the fluid. The theory is
validated through an experiment to measure the dynamic radiation force on an
acrylic sphere. Results exhibit an amplification of 66 dB in water and 80 dB in
alcohol as the difference of the frequencies is increased from 10 Hz to 240
kHz