The nonaxisymmetric acoustic field excited by a cylindrical tool placed off the axis of a fluid‐filled borehole is investigated. It is shown that the acoustic fields are composed of infinite numbers of the multipole fields with different orders. In cases in which the medium outside the borehole is an isotropic homogeneous elastic solid and a two‐phase medium, the dispersion and excitation of the mode waves such as Stoneley waves, pseudo‐Rayleigh waves, flexural waves, and screw waves are studied. The full waveforms in the time domain are also simulated and analyzed. It is pointed out that the components of the symmetric and nonsymmetric acoustic fields could be strengthened or weakened by adding and subtracting the two full waveforms logged in some opposite azimuths in a horizontal plane. A method of extraction of the shear wave is presented, and the relationship of the nonsymmetric acoustic field to the shear wave logging is analyzed.