High-frequency (8 to 16 kHz) reference thresholds and intrasubject threshold variability relative to ototoxicity criteria using a Sennheiser HDA 200 earphone

Objective: The first purpose of this study was to determine high-frequency (8 to 16 kHz) thresholds for standardizing reference equivalent threshold s ound pressure levels (RETSPLs) for a Sennheiser HDA 200 earphone. The secon d and perhaps more important purpose of this study was to determine whether repeated high-frequency thresholds using a Sennheiser HDA 200 earphone had a lower intrasubject threshold variability than the ASHA 1994 significant threshold shift criteria for ototoxicity. Design: High-frequency thresholds (8 to 16 kHz) were obtained for 100 (50 m ale, 50 female) normally hearing (0.25 to 8 kHz) young adults (mean age of 21.2 yr) in four separate test sessions using a Sennheiser HDA 200 earphone . Results: The mean and median high-frequency thresholds were similar for eac h test session and increased as frequency increased. At each frequency, the high-frequency thresholds were not significantly (p > 0.05) different for gender, test ear, or test session. The median thresholds at each frequency were similar to the 1998 interim ISO RETSPLs; however, large standard devia tions and wide threshold distributions indicated very high intersubject thr eshold variability, especially at 14 and 16 kHz, Threshold repeatability wa s determined by finding the threshold differences between each possible tes t session comparison (N = 6), About 98% of all of the threshold differences were within a clinically acceptable range of +/-10 dB from 8 to 14 kHz, Th e threshold differences between each subject's second, third, and fourth mi nus their first test session were also found to determine whether intrasubj ect threshold variability was less than the ASHA 1994 criteria for determin ing a significant threshold shift due to ototoxicity. The results indicated a false-positive rate of 0% for a threshold shift greater than or equal to 20 dB at any frequency and a false-positive rate of 2% for a threshold shi ft >10 dB at two consecutive frequencies. Conclusions: This study verified that the output of high-frequency audiomet ers at 0 dB HL using Sennheiser HDA 200 earphones should equal the 1998 int erim ISO RETSPLs from 8 to 16 kHz, Further, because the differences between repeated thresholds were well within +/-10 dB and had an extremely low fal se-positive rate in reference to the ASHA 1994 criteria for a significant t hreshold shift due to ototoxicity, a Sennheiser HDA 200 earphone can be use d for serial monitoring to determine whether significant high-frequency thr eshold shifts have occurred for patients receiving potentially ototoxic dru g therapy.