Speeds of sound and densities of binary mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide with acetonitrile or with tetrahydrofuran have been measured within the temperature range of (298.15 to 313.15) K. From these experimental values, some related quantities have been derived, such as adiabatic compressibility coefficients, kappa(s), excess molar volumes, V-E, excess molar compressions, K-S(E), apparent molar volumes, V-phi, partial molar volumes, (V) over bar (i), excess partial molar volumes, (V) over bar (E)(i), and apparent molar adiabatic compressions, K-S,K-phi. It has been found that concentration dependence of speed of sound in investigated systems resembles that of surface tension. Also, it has been observed that excess molar volumes and adiabatic compressions of some shorter chain 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides in mixtures with the same solvent are very similar.