The hearing loss simulation is based on two algorithms which simulate recruitment  and spectral smearing .
 Moore, Brian, and Glasberg, Brian (1993): Simulation of the effects of loudness recruitment and threshold elevation on the intelligibility of speech in quiet and in background of speech. J. Acoust. Soc. Am, 94(4), 2050:2062
 Baer, Thomas, and Moore, Brian (1993): Effects of spectral smearing on the intelligibility of sentences in noise. J. Acoust. Soc. Am, 94, 1229:1241