He's blind but his hearing is better than most people's.
"Acute" sounds scientific/medical. So if the speaker is a doctor and/or a scientist then "more acute" works all right too.
"Keen" and "keener" aren't really used much. The only times I've heard the word "keen" in the last few years is on the Blacklist TV series (as in Agent Elizabeth Keen). So people will totally understand you, but at the same time "keen" might seem just a bit odd or idiosyncratic.
The Language Level symbol shows a user's proficiency in the languages they're interested in. Setting your Language Level helps other users provide you with answers that aren't too complex or too simple.
Has difficulty understanding even short answers in this language.
Can ask simple questions and can understand simple answers.
Can ask all types of general questions and can understand longer answers.
Can understand long, complex answers.
This answer was given within 60 minutes of the question being posted.
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