Headphones vs. Earphones

[pennywill]

I have a couple sets of 'noise canceling' headphones. They take power and generate frequencies out of phase with the noise going on around you. They work well when it's a constant sound such as aircraft engines. They also boost some frequencies to equalize the sound. They don't work well with varying sounds, but are great for car travel (as an oblivious passenger). If you don't turn on the canceling, they work as regular headphones.