A method and apparatus for the reduction of sound travelling in a wave-guide in the air above the ground is presented, comprising the provision below the ground of at least a top layer which, at the interface of the top layer and air, has an acoustic impedance which substantially matches the acoustic impedance of the air. Also a cylindrical structure with holes can be used. The method and apparatus may be used for the reduction of aircraft sounds, especially in the range of 15 Hz to 40 Hz, during the first part of take-off, wherein said layer(s) below the ground are provided in a range starting at a lateral side of the runway and extending until at least 100 meters, preferably until at least 300 meters and more preferably until at least 500 meters, from the runway.