The term UCL fits the measurement better than LDL, yet US practice favors LDL

Evidence

Note that there are other terms in operation with the same meaning as LDLs: uncomfortable loudness levels (UCLs or ULLs) or threshold of discomfort (TD). Which term to use is a large discussion among scientists and professionals. If one follows the convention to use the term that corresponds with the measurement, UCL or ULL is probably more appropriate than LDL or TD, because patients are typically asked to find a level at which sound is uncomfortable. That being said, it is most common in the United States to use LDL. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 861

Categorization

• DEFINE: Clarifies the overlapping terms LDL, UCL, ULL, and TD and which best matches the measurement.