Here is a way to lessen the noise coming into your home or office from the outside - just integrate noise canceling technology into your windows. Tech Digest links to a Discovery News item on just such a technology in development. Sound proofing buildings is a technical challenge, particularly when they are near low frequency noise sources, like airports, rail lines, and highways/motorways. Low frequencies are harder to block as it take a lot of mass to absorb those sounds, compared to high frequency ones.
So, how are Thilo Bein, head of the business unit for energy, environment and health at Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt, Germany and his team doing it? Their solution is to use piezoelectric materials to vibrate the surface of the window glass so that it destructively interferes (i.e. cancels out) the noises trying to get through the glass, similar to how noise canceling headphones reduce the low frequency sounds on board an aircraft that try to get past the headphones and into the wearer's ears.
This is pretty neat idea which uses the strengths of noise canceling technology (which is good at reducing low frequency noises, but not so good at high frequencies) to solve a problem of our modern, urbanized and mechanized world.