What does the coupling medium affect in ultrasound testing?

The coupling medium plays a crucial role in ultrasound testing as it facilitates the transmission of ultrasonic waves between the transducer and the material being inspected. The choice of coupling medium can significantly influence the sensitivity to small defects.

When using a proper coupling medium, it minimizes the acoustic impedance mismatch between the transducer and the test material, ensuring that more ultrasonic energy is transmitted into the material rather than being reflected back. This increased transmission enhances the ability to detect small defects, as these defects will create more noticeable reflections or echoes in the ultrasonic signal.

If the coupling medium is inadequate or improperly applied, it can lead to poor signal transmission, resulting in lower sensitivity and potentially missing smaller flaws that could be critical to the integrity of the material. Therefore, a good coupling medium is essential for optimal detection capability in ultrasound testing, particularly for identifying small defects.