In this letter, a complete model and experimental verification of the nonlinear acousto-optic coupling between a co-propagating core and lowest-order cladding modes in tapered fiber optics are presented. The methodology presented in previous works have been extended to construct a full model, based on the local bending effect to compute the linear and nonlinear variations in the refractive index, which explains the influence of the acousto-optic effect in nonlinear pulse propagation. We show that there is good agreement between the results of the model and experiment.