2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/24482We point out that the velocity of propagation of sound wavepackets in a Bose-Einstein condensate filling a three-dimensional cubic optical lattice undergoes a maximum with increasing lattice depth. For a realistic choice of parameters, the maximum sound velocity in a lattice condensate can exceed the sound velocity in a homogeneous condensate with the same average density by 30%. The maximum falls into the superfluid regime, and should be observable under currently achievable laboratory conditions.6 pages, 2 figures, accepted for publication in Europhys. Lett. http://www.epletters.ch/Soft Condensed Mattertext