This study was explored utilizing both forehead and mastoid positions of bone oscillators in order to verify the clinical effectiveness on positions of bone oscillators. Sixty adults, 20 (40 ears) with normal hearing, 20 (40 ears) with conductive hearing loss and 20 (40 ears) with sensorineural hearing loss participated in the study. Pure tone audiometry was performed with air conduction (AC),
bone conduction at mastoid (BCm), and bone conduction at forehead (BCf) thresholds. The results of this study were as follows：
1) Comparison among transducers, the thresholds of AC, BCm and BCf, showed statistical significance at three groups.
2) The threshold difference of three transducers in three groups showed statistical significance except AC-BCf of normal hearing and sensorineural hearing loss groups.
3) The threshold difference of BCf-BCm at normal hearing, conductive hearing loss, and sensorineural hearing loss groups were 10.1, 7.4, 7.4 dB, respectively.
4) Considering the lowest threshold at BCm, less BCf-BCm threshold difference in conductive hearing loss and frequency characteristics of BCf-BCm threshold difference, the forehead position is less influenced by osseotympanic bone conduction and inertial bone conduction than the mastoid position. It seems that forehead placement is more suitable for inner ear measurement than mastoid placement. However, the data in this study are limited in providing the standardized force for the forehead measurement and more data should be collected for better understanding of bone conduction mechanism.
KEY WORDS：Bone conduction·Forehead·Mastoid.