In this study, it is assumed that the velocity of the BM (VBM) is related to the hearing threshold in both air-conducted (AC) and bone-conducted (BC) hearing. The AC stimulation was implemented by assigning a uniformly distributed dynamic unit pressure on the surface of the tympanic membrane (TM). Boundaries of the head and auditory periphery components, such as the ends of the ligaments and tendons, edge of the tympanic annulus, and outer bony shell of the cochlea, were fixed. On the other hand, the BC excitations were implemented by assigning a sinusoidal force on the screw component in the typical position for a bone-anchored hearing aid (BAHA). The screw component was inserted perpendicular to the skull surface at the BAHA position. The direction of the sinusoidal force was determined as the direction in which the screw component was inserted. Figure 3 shows the stimulus methods for AC and BC hearing as well as the directions of the corresponding sinusoidal forces. All the simulations were performed using the commercial software ACTRAN (MSC Software, Newport Beach, CA, USA) in the frequency domain from 0.1 to 10 kHz in 0.1 kHz increments.
To obtain the BF map of the current FE cochlear model, the BM velocities were calculated at about 180 positions (every about 0.2 mm from the base to the apex) along the BM length at each simulated frequency. Based on these calculated velocities, the specific position showing the maximum velocity among the 180 positions corresponding to an input frequency was defined as the ‘BF position’. In addition, since the BF position is the same between the normal and the specific condition except when the input frequency is different, the hearing loss (or gain) was calculated by the difference in BM velocities at the BF position according to the input frequency between the normal and the specific condition (e.g., otosclerosis).
To obtain the BF map of the current FE cochlear model, the BM velocities were calculated at about 180 positions (every about 0.2 mm from the base to the apex) along the BM length at each simulated frequency. Based on these calculated velocities, the specific position showing the maximum velocity among the 180 positions corresponding to an input frequency was defined as the ‘BF position’. In addition, since the BF position is the same between the normal and the specific condition except when the input frequency is different, the hearing loss (or gain) was calculated by the difference in BM velocities at the BF position according to the input frequency between the normal and the specific condition (e.g., otosclerosis).
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