Acoustic parameters such as acoustic impedance, intermolecular free length, adiabatic compressibility, relative association, and Gibb’s free energy of polyethylene glycols of molecular weight 200 and 600 in methanol butylparaben solution were investigated using ultrasonic velocity and density measurements at temperatures T=293.15 and 298.15k and experimental pressure p=0.1MPa. The acoustic parameters adiabatic compressibility and intermolecular free length obey the same pattern as these measured parameters; however, the parameter acoustic impedance follows the opposite trend. In the current scheme under investigation, there are strong interactions between the solute and solvent molecules.