There are many techniques available to study physical properties to interpret the molecular interaction in liquids, liquid mixtures and solutions. The study of ultrasonic waves through solution is found to be quite interesting. The study of ultrasonic waves through solution is used for knowing the nature and strength of intermolecular forces and their interaction in liquids, liquid mixtures and solutions. Thermo-acoustical and its allied properties are very helpful in predicting the physico-chemical behavior and molecular interactions occurring in liquids, liquid mixtures and solutions. Hence this motivates the researchers to take up the research project in the field. Ultrasonic velocity, density and viscosity have been measured for antibiotic ampicillin sodium in water at different concentrations, temperatures and different frequencies such as 2MHz, 4MHz and 6MHz, with a view to investigate the exact nature of molecular interactions. From the experimental data, ultrasonic parameters such as relative association, specific acoustic relaxation time and free volume have been computed. The results have further been used to interpret the nature and strength of molecular interactions in the aqueous solution of ampicillin sodium.