  In this paper we study dark solitons in quasi-one-dimensional Bose-Einstein
condensates (BECs) in presence of an anharmonic external potential. The
theoretical model is based on the Mu\~noz-Mateo and Delgado (MMD) equation that
describes cigar-shaped BECs with repulsive interatomic interactions. Since MMD
equation presents a nonpolynomial form, the soliton-sound recombination cannot
display the same pattern presented in the cubic model. We perform numerical
simulations to compare both cases.
