The present inventive concept relates to an interference noise-control unit, for installation on a sound arresting wall for reducing noise from trains or cars. The interference noise-control unit comprises: a housing to be secured on a sound arresting wall. The housing comprises a hollow compartment comprising at least one first channel and at least one second channel, wherein the first channel has a first channel height A and a first channel length B, and wherein the second channel has a second channel height A′ and a second channel length B′, and wherein the first channel height A is different from the second channel height A′.

Diffractor for diffracting sound of traffic on a travel surface with at least one diffraction plate disposed laterally beside the travel surface. The diffraction plate is provided with a pattern of recesses in the upper surface thereof for the purpose of diffracting the traffic noise in a direction which differs from the lateral direction. Each of the recesses is divided into individual resonators by intermediate walls provided in the recesses. The recesses have acoustically substantially non-absorbing walls and are free of acoustically absorbing material. The intermediate walls between adjacent resonators have at least one throughflow opening along which the rainwater can flow from the one resonator to the other.

The disclosure relates to an interference noise-control unit comprising a housing to be secured on a sound arresting wall. The housing comprises a hollow compartment comprising at least one first channel and at least one second channel, wherein the first channel has a first channel height A and a first channel length B, and wherein the second channel has a second channel height A and a second channel length B, and wherein the first channel height A is different from the second channel height A.

Reconfigurable acoustic metamaterials, reconfigurable noise barriers, and methods of tuning noise barriers. A reconfigurable acoustic metamaterial for a noise barrier includes one or more phononic crystals formed with a two-dimensional phase-transforming cellular material. A reconfigurable noise barrier may be formed with the reconfigurable acoustic metamaterial. The phase-transforming cellular material allows the phononic crystals to be tuned by applying in-plane forces to either expand or collapse the two-dimensional phase-transforming cellular material two-dimensionally in the plane of the phase-transforming cellular material.