Borehole sonic measurements provide relevant dynamic elastic properties of rock formations surrounding a wellbore. Shoulder-bed effects, in addition to near-wellbore heterogeneity often influence the interpretation of sonic measurements. To date, the interpretation of sonic measurements acquired under complex geometrical conditions remains challenging because of lack of fast numerical-simulations algorithms. We develop multifrequency 1D axial and 2D axial-radial spatial sensitivity functions to

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... rapidly simulate borehole propagating modes in the presence of wireline and LWD sonic tools. The sensitivity functions quantitatively define the volume of investigation for particular modes, whereby they serve as weighting filters to linearly approximate dispersion curves. Modeling examples are considered of sonic measurements acquired across thin beds with invasion to verify the accuracy and reliability of the new rapid simulation approach. Comparison of results to finite-element calculations confirms that efficiency and accuracy of the new approximation.