Sparse trial counts can still yield accurate loudness functions via estimation theory.

Evidence

The ISO adaptive recommendation for CLS testing results in a relatively low number of experimental trials (≈ 15–30), in order to reduce the testing time and make the test more clinically realizible. Although this is an efficient approach, due to the low number of samples, the resulting CLS function can be inaccurate. The ML estimate of a listener’s loudness perception based on this lower number of experimental trials is able to more accurately predict a listener’s underlying CLS function, without removing outliers or using assumptions about the shape of the function to smooth the result. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2565