Minimal time to determine direction of azimuthally moving sounds in moderately severe sensorineural hearing loss

Minimal time (MT) to determine direction of the broadband (0.2-8 kHz) sound source motion was measured in 12 patients with symmetrical moderately severe sensorineural hearing loss (SNHL) and 11 normally hearing listeners. For the aim we used an adaptive psychoacoustic procedure and a free field model of azimuthally moving sound sources based on the precedence effect. Patients showed high between-individual variability of MT (200-1500 ms) despite the fact that they had equal hearing loss degree. Median value of MT in SNHL patients was tenfold higher than in subjects with normal hearing: 1000 and 100 ms, respectively. The results indicate that impaired hearing sensitivity per se is not the main factor influencing perception of azimuthal motion in SNHL patients. Possible reasons of the revealed temporal deficit are loss of compressive nonlinearity of the basilar membrane, effects of age and SNHL duration. The latter can also lead to central auditory processing disorders and subsequent worsening of temporal analysis.