Which headphones should be purchased?

Agree with Mezmo re: Etymotics. I have a pair of the ER-4S and highly recommend them. They are not cheap. They look similar to an earplug and offer fidelity that is simply remarkable for its design. The other great benefit is that they also attenuate external noise such as jet engine or rail noise which allows one to relax and feel much perkier when he arrives at his destination.

Check 'em out. Might just be the ticket for your needs.

Headroom also has some recommendations on headphones for noisy environments.

When I was a traveller, I used to use sony nc-20 noise cancelling headphones. They didn't cancel as much noise as I wanted, and the fidelity was 'just ok'. They were best at cutting out low droning noises like a bus or jet engine. The metal backed sony mdr-v6's were almost as good at shutting out noise. Both headphones are reasonably small and comfortable to wear. The v6's were more rugged, the nc-20's folded up very small. Neither one of these can hold a candle to my senn 580's.

I never tried the etymotics. I was a little concerned with having a speaker THAT close to my eardrum.

I have a pair of Etymotics 4S and a Headroom Amp. Noise cancellation is second to none. Sound quality is a good as any headphone period, it's all personal prefernce. When you have great noise cancellation, you won't have to play your music at highter levels to cancel out the noise to enjoy your music. I would not worry about hurting your eardrums. The negative is that the 4S's need an exteral amp. However, Etyomotics makes a version that does not require an amp that is very close to the sound quality of the 4S called the 4P.

Suggest you check out the forums at headwize.com and headfi.org. Use their search engine and you should find some useful info. I would avoid the Bose headphones. For traveling I use cheapo noise cancelling headphones which stink sonically. In the fall and winter, I usually use Grado RS-2 headphones, which I personally prefer over the Sennheisers. The Sennheisers are good, but too difficult to drive compared to the Grados and Ultrasones. In the summer, when the a/c is on and I want some isolation I use the Ultrasone HFI600. This particular Ultrasone is a sealed back headphone and is the only sealed phone I have found that rivals an open back phone in spaciousness and soundstaging. I have tried various sealed headphones such as Sennheiser, Sony, Koss and Denon but have found nothing that rivals the Ultrasones, which are not widely distributed or well known. They are mostly sold in the US thru pro audio dealers or are available at meier-audio.com. Tonally, they are to headphones what the Spendors are to loudspeakers. Yes, they are even a little smoother sounding than the Grados. You may not like the way they look either. However, for plugging directly into a portable and for a sealed back phone, I have found nothing better. I think Ultrasone may have changed the design of the HFI600 since I got mine and the current model looks better and folds up, but may not be as comfortable. Good luck and enjoy.