thread I briefly used something
similar in one of the datacentres I used to work in and chucked them because yes they took away the server noise but the result was all I could hear was my heartbeat which while comforting to know the ol' ticker was still going ended up being very disconcerting and offputting.
permalink None of these seemed nearly that good
But I guess in a noisy Dixon's (which I just realised still exist in airports only) and with demonstration models that have probably been messed around with... Perhaps it wasn't ideal

permalink For budget, apparently Samsung
permalink They're good with steady, constant noises like planes
Not so much with people talking noises because they're constantly changing