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Quantifying air-conducted acoustic radiation from the bone-conduction vibrator
1Department of Communication Sciences and Disorders, The University of Texas at Austin, 78712-1089, USA.
Journal of the American Academy of Audiology
|December 29, 1998
Summary
Bone-conduction testing can produce false air-bone gaps due to acoustic radiation. Placing the vibrator on the forehead or contralateral mastoid minimizes this artifact, especially at 4000 Hz.
Area of Science:
- Audiology
- Hearing Science
- Biomedical Engineering
Background:
- Bone-conduction (BC) testing is crucial for diagnosing hearing loss.
- Acoustic radiation from the BC vibrator can influence sound pressure levels in the ear canal.
- The osseotympanic mode of BC can be affected by sound reaching the external auditory canal.
Purpose of the Study:
- To investigate sound pressure levels in the ear canal during BC testing.
- To determine the impact of vibrator placement on acoustic radiation.
- To identify conditions leading to false air-bone gaps.
Main Methods:
- Measured sound pressure levels in 50 subjects' ear canals at 2000 and 4000 Hz.
- Utilized a bone-conduction vibrator placed on the forehead, ipsilateral mastoid, and contralateral mastoid.
- Used an ear canal plug to minimize osseotympanic BC effects.
Main Results:
- Clinically significant false air-bone gaps (>10 dB) are likely at 4000 Hz with ipsilateral mastoid placement.
- Acoustic radiation into the concha is the primary cause of these false gaps.
- Forehead or contralateral mastoid placement reduces confounding acoustic effects.
Conclusions:
- Vibrator placement significantly impacts BC test accuracy.
- Forehead or contralateral mastoid placement is recommended to minimize acoustic radiation artifacts.
- Masking the non-test ear is advised when using contralateral mastoid placement.