The Clear Harmony NC200 noise-canceling headphones from Able Planet are foldable, which is always nice when you want to tuck them away. They feature LINX AUDIO which accomplishes all of the noise-canceling with a frequency response of 20-20,000 Hz. It has a sensitivity of 1 Hz. A single AAA battery will power these headphones. The Clear Harmony NC200 headphones are available from Amazon for just $99.