Ultrasonic velocity, density, and viscosity have been measured in the binary mixtures of nitriles with (CH3OH/C6H5CH3) at different temperatures. Excess thermodynamic functions that have extensive applications in the characterizing aspects of the physico-chemical behaviour of liquid mixtures are evaluated. Other useful thermo-acoustical parameters, which can compliment the study of molecular interactions in binary mixtures, are also evaluated. An analysis of the thermo-acoustical parameters and excess thermodynamic functions suggests the presence of a strong intermolecular interaction in all four binary mixtures and a stronger, specific interaction in (C6H5CN + CH3 OH) mixtures.