Perfect hearing. I've just had a hearing test.
The right ear is good for my age (65)
Left ear? -65dB at 4kHz
It's a long term issue getting worse with age. 7 years ago it was -40dB at 4kHz
The audiologist was very thorough. First the test with headphones (earbuds, actually). Repeated using bone conduction from behind each ear. (This is to see if the problem is in the middle ear.) Repeated again on the left with white noise injected on the right so I could not hear across my scull. With interference the two curves leaft earbud and left bone conduction - matched. Middle ears OK. Problem in left cochlea or neural pathway - but I knew that!
Now the easy way to audio-borg must be a vibrator implanted behind each ear - but it wouldn't help me. I would need direct brain injection.
More difficult! Especially if you can't locate the brain.
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More down to earth question:
What does -65dB at 4kHz in one ear mean for enjoyment of (recorded) music; and for the choice of loudspeakers?
I don't need a super-tweeter!