Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

2.12: The Sound Fields
2.12.1 Wave Interaction or Interference
Before we move into the next section, the subject of wave interaction must
be covered since it is important when trying to understand the performance
of an ultrasonic transducer. On the previous pages, wave propagation was
discussed as if a single sinusoidal wave was propagating through the
material. However, the sound that emanates from an ultrasonic transducer
does not originate from a single point, but instead originates from many
points along the surface of the piezoelectric element. This results in a
sound field with many waves interacting or interfering with each other.