Ultrasonics is the study and application of sound waves with frequencies above the range of human hearing, typically above 20 kHz. This field is used in a wide range of applications, including medical imaging, industrial cleaning, non-destructive testing, and measuring the properties of materials. Ultrasonic waves can be used to detect flaws or defects in materials, create images of internal structures, and even manipulate particles at a microscopic level. Overall, ultrasonics is a versatile and valuable technology that has a wide range of practical applications.