A booster is an acoustic tool used in ultrasonic welding that amplifies and transmits vibrations from the ultrasonic transducer to the horn. The booster is designed to provide mechanical advantage, and it changes the amplitude of the vibration that is transmitted to the horn. The booster typically has a threaded attachment that connects to the transducer, and a similar attachment that connects to the horn. Boosters come in a variety of shapes and sizes, and are often made of materials such as aluminum, titanium, or steel. The selection of a booster depends on the specific application, and factors such as the material being welded, the frequency of the ultrasonic vibration, and the size and shape of the horn.