Graphene is known as thinnest, strongest and most durable material in the world. Due to its unique electrical, mechanical and optical properties, it is an ideal nanofiller for various polymers and discovering new composites. The functionalization of graphene with polymer can be achieved in several ways, including ultrasound. This study presents the influence of ultrasound on the functionalization of graphene with polyvinyl alcohol and is based on pressure measurements in the flask during the process, under the influence of ultrasonic cavitation. Based on the results, an explanation of the sonochemical effects reported in the literature is given.