snowite, I think what you’re saying matches my understanding. With the bone conduction test the sound is going straight to the cochlea. If you can’t hear the sound, it’s because of damage to the cochlea or the auditory nerve.
With the air conduction test the sound has to travel down the ear canal, vibrate the ear drum, and then vibrate the three bones in the middle ear before the sound gets to the cochlea. So wax in the ear canal, a ruptured ear drum, gooey mucous in the middle ear or excess deposits of bone in the middle ear could all stop the sound, and that would be a conductive loss.
I am not a doctor!
They told me they want to see a pretty big gap between the air conduction scores and bone conduction scores before they’ll recommend surgery for otosclerosis. I can’t remember if they specified at least 15, 20, or 25 dB as the gap size.
In my left ear my scores were:
500 Hz Air 100 Bone 50
1000 Hz Air 90 Bone 55
2000 Hz Air 80 Bone 65
4000 Hz Air 100 Bone 50
Only my left ear has otosclerosis. In my right ear, the air and bone scores were identical at some frequencies and about 5 dB apart in some. After surgery in my left ear my scores came up to 5 dB below the original bone conduction scores, except at 2000 Hz, which came up to 45 dB compared to the 55 dB I had hoped for – a nice surprise.
After the surgery I got hearing aids and I am hearing in the normal range now. I really didn’t expect that and I’m very pleased.