The speed of sound can be considered to evaluate acoustical parameters and hence, to investigate physico-chemical properties of drug polymer suspension. Investigations of these physico-chemical properties enable to understand the nature and strength of particle-liquid interactions. The suspensions were made up of a 1:1, 1:2, 1:3, 1:4, 1:5 mixtures by weight of drug Risperidone and Polyethylene Glycol by using ultrasonic probe sonicator. The product was further characterized by using techniques such as scanning electron microscopy (SEM), fourier transform infrared spectrocopy (FTIR). Ultrasonic velocity, density, and viscosity have been measured for different suspension at different temperature ranging from 283 K to 323 K. Different acoustical parameters, such as adiabatic compressibility, relaxation time, acoustic impedance, are evaluated from experimental data. It is found that drug-polymer interaction increases significantly for 1:3 ratios, which indicates formation of cluster and strong drug polymer interaction.