My wife wants to listen to mp3s in her tractor, there's a head unit in there but you'd need to really crank it up to be heard over the engine. I'm thinking noise cancelling headphones could be the way forward, she's never previously had even a tape walkman so has never used 'phones, I hardly ever use them either, but in my limited experience I've never got on with in ear ones like these:

http://tinyurl.com/onrduj

I used to find the old Rio Karma ones comfortable but can't see any like that on there. Most of the external ones are huge.

Any recommendations? A thought that's just occurred to me is whether she should be listening to music at all, she'll be adding more noise to an already noisy environment for 3-4 hour stints, should she be worried about her hearing, and would noise cancelling be better or worse in this regard?