In ultrasonic welding, a nodal point is a point on the ultrasonic horn or booster where there is minimal or zero amplitude of vibration. This is because at the nodal point, the wave amplitudes coming from the horn and the booster are out of phase and cancel each other out. Nodal points are important to consider when designing the ultrasonic welding process, as they can affect the location and quality of the weld. The location of nodal points can vary depending on the design and dimensions of the horn and booster.