A comprehensive mechanical characterization of the wellbore rock relies on a three-dimensional (3D) characterization of the compressional and shear slowness in terms of their radial, azimuthal, and axial variations. These rock property variations arise because of non-uniform stress distributions, mechanical or chemical near-wellbore alteration due to the drilling process and formation intrinsic anisotropy in shales. The critical data required to invert for these parameters is derived from broadband dispersion curves of propagating borehole acoustic modes. The new modular sonic tool incorporates improved monopole and cross-dipole transmitter technology while featuring an extensive receiver array incorporating 13 axial levels of 8 azimuthal sensors each. Each receiver is individually digitized resulting in 104 waveforms leading to a more reliable and accurate slowness estimation than with the previous technologies. This comes about in particular through improved borehole mode extraction/rejection and enhanced wavenumber resolution at all frequencies. In this paper, we highlight unique features of this new tool that have an important impact on seismic and borehole seismic problems. The high quality waveforms and advanced processing techniques lead to improved compressional and shear slowness estimates, radial profiling of shear and compressional slowness, enhanced anisotropy detection and mechanism identification, and reliable through casing slowness measurements. Examples are shown from various wells around the world.