Steady state responses to multiple amplitude-modulated tones: an optimized method to test frequency-specific...

To evaluate, using statistical methods, the usefulness of the binaural multiple frequency auditory steady state responses (MF SSRs) for objective, frequency-specific audiometry in a large sample of hearing-impaired children and normal-hearing subjects.

The MF SSRs were recorded in a sample of 43 hearing-impaired children (86 ears) and 40 normal-hearing young adults (80 ears). Simultaneous carrier tones (0.5, 1, 2, and 4 kHz) modulated in amplitude at different rates (77 to 105 Hz) were presented binaurally (TDH 49 earphones) at variable intensities (110 to 20 dB SPL). For each subject the response thresholds (RTHs) at 0.5, 1, 2, and 4 kHz, were determined automatically (F test) and compared with the corresponding behavioral thresholds (BTHs).

In the normal-hearing subjects, RTHs were detectable, on average, between 11 and 15 dB above the BTH. These differences were significantly smaller in the hearing-impaired (5 to 13 dB). Also a close correspondence was found between the subjective and objective audiogram curves in both groups. The within subject Spearman correlation coefficients calculated between the two curves, were in most cases above the significance cut off point (p < 0.05). Also in 1-way repeated measures analysis of variance, the overall error in the estimation of the audiogram (vector across frequency of absolute distances between the curves) did not differ significantly from zero.

The binaural MF SSR was proven to be a valid technique for the estimation of an objective audiogram, in a large sample of hearing-impaired children and normal-hearing subjects. With this method, frequency-specific thresholds at 0.5, 1, 2, and 4 kHz could be determined in all subjects (and both ears) with no appreciable loss in accuracy and a considerable reduction in testing time (average recording time = 21 minutes) when compared with other frequency-specific techniques.