Pulse-Echo Ultrasonic Tandem Technique

This is the through-transmission testing with two probes. A transmitter sends sound through the component, and the receiver on the other side measures how much gets through. If there's a flaw in the path, less sound passes. It works best on smooth, parallel surfaces and when you can access both sides. The angle and distance between the probes are critical, so you must follow the test procedure and couple properly, otherwise you'll get bad readings.