The sony mdr-7506 is an extremely sensitive, closed, isolating headphone that's great for travel and monitoring professional field recordings especially dslr video.
because the headphone is small, light, rugged, sounds pretty good, is extremely sensitive for use with dslrs, ipods and portable digital and video recorders, it does a good job at isolating outside noise, it leaks very little sound to the outside, folds for carrying, and you even can flip over the earpieces to use just one side at a time held to your head if you're singing in a studio with live performers.