DD9 has always seemed a bit noise-sensitive, but we've never done much about it (OK, realizing that makes me sound like a terrible parent!). When she was small, she would get very upset in public restrooms about toilets flushing or the air dryer sound (covering her ears). She has played basketball and she spends the last 30 seconds of every quarter standing still watching the clock run down...covering her ears before the buzzer went off (no, she is not a very serious player).
Honestly, it has improved as she has gotten older. Also, she was never terribly anxious about it - if she had been, we may have explored more options.
