A concrete wall that separates a highway from the associated environs to dampen the noise pollution to surrounding areas. These are found in urban and suburban areas where a freeway or other highway travels through a residential zone. They also provide a function of security to prevent pedestrians from entering the freeway right-of-way. In some cases, a sound barrier may only consist of a wooden stockade fence. Most new sound barriers feature a motif that reflects a city's culture or history.