What sensitivity issue is associated with early through-transmission ultrasound-based techniques?

The sensitivity issue related to early through-transmission ultrasound-based techniques primarily revolves around the detection of small defects and discontinuities. In these techniques, the ability to effectively transmit ultrasound through a material and accurately assess its internal structure can be significantly challenged by minor imperfections.

Through-transmission methods rely on sending an ultrasound signal from one transducer, through the test material, to a receiving transducer on the opposite side. When the defects or discontinuities are smaller than a certain threshold, their impact on the transmitted signals may be negligible, making it difficult to identify them. This sensitivity issue is especially pronounced in materials with complex geometries or when facing challenges like attenuation and scattering due to the material properties.

The other factors listed may influence the overall inspection process but do not specifically highlight the sensitivity challenges unique to the detection of small defects or discontinuities. For instance, while joint geometry and the orientation of the inspected part can affect sound transmission paths, they do not diminish the inherent limitations of early through-transmission methods in identifying small flaws. Similarly, the choice of coupling medium is important for ensuring effective energy transfer but does not specifically relate to the sensitivity of detecting fine defects.