This chapter gives an introduction to acoustic technologies, particularly focused on how acoustic waves are generated in piezoelectric crystals and how that can be used for the development of biosensors. Secondly, a detailed explanation of the fabrication of acoustic wave devices is given, including materials used for construction and vibration modes of different devices. Thirdly, the most common types of acoustic sensors are described—quartz crystal microbalance, acoustic plate wave devices, surface wave sensors, and flexural plate wave devices. Also, for the quartz crystal microbalance a detailed description of the physical models developed to quantify the mass loading from the acoustic response is presented. Finally, a brief account of the acoustic sensors applications is presented, both industrial and in the biosensing arena.