In ultrasonic testing, the near field (also known as the Fresnel zone) is a critical region directly in front of the transducer where the ultrasonic beam undergoes complex interference patterns.
This calculator helps NDT technicians visualize and calculate the near field length for their specific transducer setup. By adjusting the transducer diameter, frequency, and material velocity, you can determine where the near field ends and the far field begins.
This is crucial because amplitude measurements in the near field are unreliable due to the complex interference patterns, so defect sizing and evaluation should typically be performed in the far field region. The blue shaded area shows the interference pattern, and the red dashed line marks the transition point to the far field, where the beam becomes more uniform and predictable.