Paper by HAHN from ISCR 5th 1986 Aachen Germany
Roads now ofcen have to be provided wich noise control scructures, those most commonly employed being earthbanks, steep-faced banks, acoustic screens and noise reduccion barriers. Large installations and special structures for noise control purposes are more rarely encountered. "Steep-faced banks", which occupy less space than earth-banks, consist of a supporting frame-work of concrete which is filled along its whole length with earth so that horizontal surfaces, suitable for planting with shrubs, are formed in a stepwise arrangement. With suitable construction, the shrubs soon conceal the concrete structure so that the visual impression of a green wall is obtained. Despite their higher cost, steep-faced banks providing "natural" noise control facilities with high sound reduction capacity and requiring no maintenance have been extensively adopted in the Federal Republic of Germany. Acoustic screens usually consist of individual elements made of metal, wood or plastic which are mounted on steel supporting structures. They are adopted in cases where lightweight noise control walls of large area have to be erected close to the road. Noise reduction barriers are assembled mainly from concrete elements mounted between supporting structures, mostly beams, likewise made of concrete, which is an especially suitable material for the purpose because of its many design possibilities. Such barriers should be adapted to their surroundings and, as far as possible, be concealed by dense plant growth, so that they remain visually unobtrusive. Free-standing walls require structural and aeschetic design creatment and colouring, for which there are numerous possibilities. All noise control facilities must be carefully planned because, depending on their type and size, they have psychological effects which must not be overlooked. "Nacural" solutions incorporating grassed and planted surfaces are co be preferred. Whether noise control structures should be "camouflaged" or should primarily be conceived as landscaping or town planning features will depend on what "philosophy" is favoured.