If you travel or if you commute, you need noise cancelling headphones. They'll change your life. They block out so much ambient noise, letting you listen to your music or podcasts or audiobooks at a much reduced volume and preserving your precious hearing. But that noise cancelling isn't worth much if those headphones don't sound good, right? Sennheiser -- a company with some serious audio chops -- has what it says is the solution with the professional traveller's new best friend, the PXC 550.