Green Horizons

Volume 2, Number 4
Autumn 1997

Trees as noise buffers

Trees can protect your home from annoying highway noises or from other intrusive sounds such as confinement livestock. Trees and shrubs can reduce noise five to 10 decibels (reduction of approximately 50% to the human ear) if plantings are correctly designed. Some rules of thumb for these tree/shrub plantings include:
  1. Plant close to the noise source rather than close to the area to be protected.
  2. When possible use taller plants with dense foliage.
  3. Plant trees/shrubs as close together as the species will allow and not be overly inhibited.
  4. Evergreen varieties will give best year-round protection.
  5. To reduce heavy vehicle noise in suburban or rural areas:
    a) plant 65 to 100-foot-wide belts of trees.
    b) Edge within 60 to 80 feet of road center.
    c) Trees in center row should mature at minimum of 45 feet tall.
  6. To reduce noise of moderate traffic in communities plant:
    a) 20 to 50-foot-wide belts of trees
    b) edge within 20 to 25 feet of road center
    c) use 6- to 8-foot shrubs next to road and back up tree rows to a minimum of 15 to 20 feet tall.
  7. The length of the buffer should be twice as long as the distance from source to the recipient.
  8. The buffer should also extend equal distance both directions parallel to the road.

(Source: Inside Agroforestry, a newsletter from the National Agroforestry Center at Lincoln, Neb.)