THE EFFECTIVENESS OF ACOUSTIC SCREENS ON ROADS IN RELATION TO METEOROLOGICAL INFLUENCES

UEBER DIE WIRKSAMKEIT VON SCHALLSCHIRMEN AN STRASSEN UNTER BERUECKSICHTIGUNG METEOROLOGISCHER EINFLUESSE

ATMOSPHERIC PHENOMENA WHICH GIVE RISE TO ONLY MINIMAL CHANGES IN THE VELOCITY OF SOUND, ALTER THE SOUND PROPAGATION DIRECTION. TWO PARTICULAR METEOROLOGICAL PHENOMENA ARE OF NOTE: THE RISE OR FALL IN AIR TEMPERATURE DEPENDING ON THE HEIGHT FROM THE EARTH SURFACE, AND UNIFORM WINDS. THE ABSOLUTE SOUND VELOCITY IS GIVEN BY THE VECTORIAL ADDITION OF THE STILL AIR SOUND VELOCITY, AND THE WIND VELOCITY. THIS LEADS, HOWEVER, TO AN INWARD CURVING OF THE SOUND WAVES WITH SOUND PROPAGATION IN THE WIND DIRECTION AND CHANGES TO AN OUTWARD CURVING WITH SOUND PROPAGATION AGAINST THE WIND DIRECTION. THIS BENDING OR CURVING EFFECT IS THEREFORE, UNDER THE INFLUENCE OF WIND, BASICALLY DIRECTION-DEPENDENT, BUT NOT SO UNDER TEMPERATURE INFLUENCES. IN THE CALCULATION OF THE DROP IN SOUND LEVEL RESULTING FROM ACOUSTIC SCREENS, THE SCREENING COEFFICIENT Z IS PARTICULARLY SUITABLE. THE DERIVATION OF THIS IS CALCULATED IN DETAIL. FOR A PARTICULAR VALUE OF THE INVERSION, THE SCREENING EFFECT OF THE ACOUSTIC SCREEN IS NEUTRALISED, THE SOUND WAVES THEN PASS OVER THE OBSTRUCTION. THE SIGNIFICANCE OF THIS FOR ROAD TRAFFIC IS DEMONSTRATED IN EXAMPLES. IN THE CALCULATIONS A MEAN EARTH AND AIR ABSORPTION OF 1.5 DB/100 M IS TAKEN INTO ACCOUNT. FOR WIND INVERSION, IN THE CALCULATIONS ONLY THE COMPONENTS OF THE WIND VELOCITY IN THE SOUND PROPAGATION DIRECTION ARE CONSIDERED. THE SOUND PATTERN UNDER WIND INFLUENCE FOR INDIVIDUAL PASSING VEHICLES IS REPRODUCED IN VARIOUS ILLUSTRATIONS.

Language

  • German

Media Info

  • Pagination: 162-5
  • Serial:
    • Kampf dem Laerm
    • Volume: 22
    • Issue Number: 6
    • Publisher: VJF Lehmanns Verlag
    • ISSN: 0022-8249

Subject/Index Terms

Filing Info

  • Accession Number: 01304611
  • Record Type: Publication
  • Source Agency: Bundesanstalt für Straßenwesen (BASt)
  • Files: ITRD
  • Created Date: Nov 21 2010 10:01AM