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KMID : 0858620040080020133
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Korean Journal of Audiology
2004 Volume.8 No. 2 p.133 ~ p.138
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Evaluation of Hearing Thresholds in Sound Fields Using Auditory Steady-State Responses for Subjects with Hearing Aids or Cochlear Implants
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Bang Mi-Young
Chung Myung-Hyun
Choi Jae-Young
Lim Duk-Hwan
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Abstract
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Objectives: Auditory steady state response (ASSR) can offer valuable information on the degree of residual hearing in profound hearing loss since ASSR responses can provide objective frequency specific data even in low frequency regions. Thus, the method itself has the potential application in fitting hearing aids or mapping cochlear implanting devices, but sound field measurements of ASSR thresholds with hearing assistive devices have not been studied systematically. The purpose of this study was to explore the applicability of ASSR to sound field measurements of aided threshold levels in subjects with hearing aids or cochlear implants.
Methods: Patients with the age of 4 to 81 years were selected for hearing aid condition (35 ears) and for cochlear implant condition (27 ears). Pure tone audiometry and sound field ASSR thresholds were measured and evaluated for comparison.
Results: In subjects with hearing aids, average differences between PTA and true ASSR thresholds (ASSRT) were noted as 16.4, 18.4, 12.4, and 13.2dB in 500, 1000, 2000, and 4000 Hz, respectively. The same measurements between PTA and estimated ASSR (ASSRE) thresholds showed discrepancies of 1.5, 7.1, 2.5, 0.7 dB in the corresponding frequencies. Both ASSRT and ASSRE exhibited significant differences and correlation coefficients except 4000Hz range (p<0.05). However, ASSRE showed less threshold differences from PTA than ASSRT. In subjects with cochlear implants, PTA and ASSR thresholds resulted in -6.11, -5.19, -11.11, -5.74 dB average differences in 500, 1000, 2000, 4000 Hz while PTA and ASSRE thresholds showed -32.96, -20.0, -32.04, -30.19 dB of differences. Both ASSRT and ASSRE showed significant differences and correlation coefficients (p<0.05). In this group, however, ASSRT showed less threshold differences from PTA than ASSRE.
Conclusion: Sound field ASSR data showed stable responses in estimating thresholds of subjects with hearing aids or cochlear implants. The data suggested the importance of correction factors and the need for modification of current ones in estimating sound field threshold levels in ASSR. Further studies on various speaker angles, appropriate calibrations, and possibility of artifact interactions will also help to achieve reliable application of sound field ASSR on the threshold estimation in the subjects where objective measurements are required.
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KEYWORD
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Sound field ASSR, PTA, Hearing aid, Cochlear implant
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