Psychometric functions for loudness discomfort and most comfortable loudness levels

Adaptive procedures were used to determine psychometric functions for loudness discomfort level (LDL) and most comfortable loudness (MCL) for pure tones and speech using normal and hearing-impaired listeners. For the LDL, both groups demonstrated steeply rising functions with the 50% point at approximately 100 dB SPL. The MCL data resulted in two functions, one (Function A) differentiating MCL from less intense stimulus levels and the second (Function B) differentiating between MCL and more intense levels. Function A may be considered a lower bound and Function B an upper bound for MCL. For the normal listeners, the difference between the functions at 50% response ranged from 9.9 to 19.9 dB depending upon the experimental condition. For the hearing-impaired subjects, this range was restricted to approximately 4.5 dB, primarily as a result of a shift in Function A toward higher sound pressure levels.