The influence of the hydrostatic pressure on the temperature dependences of the ultrasonic velocities and attenuation coefficients is studied in the vicinity of the phase transition of BCCD crystals. The results obtained are considered within the framework of single-and two-soft-mode models. It is shown that acoustic anomalies are well explained only by the single-soft-mode model, when only one soft mode P_k, which transforms according to the two-dimensional irreducible representation A₃ of the Pnma space group, is taken into account.