Most comfortable and uncomfortable loudness levels: six decades of research

This article critically reviews the influence of such factors as psychophysical testing method, stimulus type, and instructional set on most comfortable loudness (MCL) and uncomfortable loudness (UCL) levels. Generally, research indicates that test methods and instructions strongly affect both MCL and UCL while stimulus conditions affect them less substantially. Overall, the data suggest lower reliability for MCL than for UCL and lower reliability for pure-tone MCLs than for speech MCLs. Lower MCLs are typically obtained when measured by an ascending approach, in contrast to a descending approach. Results suggest that audiological efforts should be directed toward the development of a standardized test procedure that yields adequately reliable and valid MCLs and UCLs for routine clinical use.