The European qualification system for road traffic noise reducing devices

The European qualification system for traffic noise reducing devices (NRD's) is based on an advanced framework work of ten standards. This framework is based on a "product standard" (EN 14388) which specifies the performance requirements in terms of measurable characteristics and associated test methods. Each characteristic is rated according to as system of "classes"; for this purpose, a normalised road traffic noise spectrum has been defined (EN 1793-3). Sound absorption and airborne sound insulation must be tested in laboratory using methods which can be regarded as tuned versions of the ISO 354 and ISO 140-3 ones (EN 1793-1 and 2). The same properties can also be measured in situ on installed NRD's, following a new voluntary standard (ENV 1793-5), based on an impulsive technique with the use of a MLS test signal. A similar technique can also be applied to characterise sound diffraction of "added devices" placed on the top of NRD's (ENV 1793-4). Two standards are devoted to non-acoustic performances, such as mechanical stability, fire resistance, etc. (EN 1794-1 and 2). Finally, specific standards deal with long term durability of acoustic and non acoustic characteristics (EN 14389-1 and 2).