I love my noise canceling headphones. I wear them to the movies, on planes and at concerts. A flick of the switch and extraneous sound recedes. It is heaven. Sometimes I wonder why this feature is not built into hearing aids. The technology obviously exists. Imagine that same flick of a switch at a restaurant or a noisy cocktail party. The background hum would disappear leaving only the voices loud and clear. Seriously, why does this not exist?