The primary objective of this series of studies was to determine the extent to which plant materials are capable of reducing intrusive noise, mainly that from traffic. Tape-recorded sound and live sound were used for noise sources. Measurements were made by direct instrument reading and by magnetic-tape recording. Distances in the range of 5-122 m (16-400 ft) were used. Several kinds of trees and shrubs alone and combined with solid barriers were studied. More than 20,000 individual readings were taken in the three series of experiments; the minimum was 4 and the maximum was 12 readings at each position. Each experimental point shown on the graphs represents averages of eight or more readings. Although varying atmospheric conditions pose difficulties in the measurement of outdoor sound, the reduction of sound is less affected by the insertion of barriers than the individual day-to-day measurements are; under similar atmospheric conditions, measurements were repeatable within 1 or 2 dB. Readings much beyond 91 m (300 ft) from the noise source were subject to large atmospheric-induced fluctuations of sound level and are considered less reliable than are closer readings. Results indicate that plant materials can be used effectively to reduce intrusive noise under certain conditions. They are not a panacea, however, and considerable knowledge based on experience is needed for proper application. Perhaps the best use, in the majority of cases, is a combination of trees and some form of solid barrier. Three series of experiments, which span an eight-year period, serve as the basis for this paper. (Author)

Media Info

  • Features: Figures; References;
  • Pagination: p. 35-40
  • Monograph Title: Environmental issues in transportation: Analysis, Noise, and Air Quality
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00335171
  • Record Type: Publication
  • ISBN: 0309032032
  • Files: TRIS, TRB
  • Created Date: Oct 28 1981 12:00AM