The attenuation of low-frequency acoustic energy in stripes of the low-temperature tetragonal phase of Bi-2212 ceramics is studied taking into account thedx2−y2-symmetry of the superconducting order parameter (SOP) and the dynamic analog of phase separation. The contribution to the energy density of the strain–order parameter coupling leads to a finite value of attenuation in superconductors with a peculiar SOP. The frequency and temperature dependences of attenuation are analyzed and compared with the available experimental results. It is shown that these data are an indirect evidence of the SOP symmetry: thedx2−y2-symmetry for the Bi-2212 phase and thes-symmetry for the Bi–2223 phase. The existence of an ordered low-temperature state responsible for the low-frequency attenuation peak and other anomalies in the properties of Bi-based ceramics in the temperature range 20–40 K is proposed. ©1998 American Institute of Physics.