Speed of sound is an important property in many applications and it is being increasingly used in different technological areas. In this work a database of speed of sound and density at atmospheric pressure for n-alkanes, branched alkanes, n-alkenes, aromatics, alcohols, ethers and esters were collected from the open literature. Using these data a Wada group contribution model recently proposed by us was used as the basis for the development of a new atomic contribution model to predict speed of sound for all the families of compounds investigated in this work. It is shown that the proposed model is able to predict the speed of sound for compounds of these families with deviations close to the experimental reproducibility. This work also discusses the effect of branching on the Wada's constant, pointing out the importance of new measurements for this type of compounds. (C) 2013 Elsevier B.V. All rights reserved.