Ultrasound transducers come in different shapes and sizes depending on their intended use. The main types are linear transducers, convex transducers, phased array transducers, pencil transducers, endocavitary transducers, and transesophageal transducers. Each has a distinct piezoelectric crystal arrangement and frequency that makes it suited for specific applications like abdominal, cardiac, or fetal examinations. 4D transducers allow for live 3D imaging of motion.