The term "hash" in ultrasonic testing refers to:

In ultrasonic testing, the term "hash" specifically refers to the random and unwanted noise that can appear on the display screen during a testing session. This noise can obscure or interfere with the actual signals being tested, making it difficult for an operator to accurately interpret the data. Hash is typically caused by various factors, such as electronic interference, surface conditions, or environmental noise.

Understanding hash is crucial for technicians, as it highlights the importance of having a clear signal for reliable testing. If an operator can recognize and manage the presence of hash, they can ensure more accurate readings and successful identification of discontinuities or defects in the material being tested. This makes interpreting ultrasonic data more challenging and emphasizes the necessity of proper equipment calibration and testing conditions to minimize this phenomenon.