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Our rural house is located 200 yards from an interstate highway overpass. House is parralel to interstate, and overpass is located near a corner of property. How can we reduce the noise entering the yard?

Specifics:

  • Most of the noise comes from the beneath overpass
  • Eucalyptus and oak trees block about 40% visibility of the interstate
  • No fencing exists between interstate and house
  • Exterior wall facing the interstate reflects noise back into the yard
  • Nearest neighbor is 300 yards away
  • House is very quiet inside, but yard is very loud

My own ideas:

  • Build up 6' berm of dirt on edge of property, close to interstate, and erect an 8' a 7' wooden fence on top of that
  • Plant a row of oleander close to interstate
  • Build a fence that completely blocks visibility of overpass

Another concern:

  • If a fence is recommended, should it be located closer to interstate, or closer to house?
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    Have you checked your zoning? Fence heights are usually included. I assume that is why you want to build the berm first then the 8' fence. Otherwise fencing height may be cheaper hauling in all that dirt for a berm. But I have seen this technique employed in housing divisions near me.
    – ArchonOSX
    Aug 26 '17 at 19:01
  • You're correct: in my county the AG/AR zones are limited to 7', and may be placed atop retaining walls of no more than 4' high. That's only 11'. If overpass distance to house is 600 ft and height of overpass is 20 ft, a fence height of 11' needs to be 330 ft from house to block visibility. Is there a way to know if that is tall enough?
    – Johnathan Elmore
    Aug 26 '17 at 19:42
  • Berms will do a whole lot more silencing. However the best option is probably at trulia.com...
    – Harper - Reinstate Monica
    Aug 26 '17 at 20:35
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    I'd plant a row of Colorado blue spruces (ag zones 2-6) about 10 feet apart. They'll grow to 40-60 feet tall.
    – Tyson
    Aug 26 '17 at 23:39
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If you go with trees, go with spruce: This gives you high density twig/leaf structure. Evergreen leaf trees are also possibles.

Trees don't reduce sound by a lot, factor of 2 to 4. That sounds like a lot, but it's only 3 to 6 db. 3 db is just detectable. An earth berm is the best system. Make it fairly steep on the side facing the noise so that sound is reflected up. However, trees generate their own noise -- closer to white noise without the swoosh of traffic. This will help mask the freeway noise.

Material for a berm can come from creating a pond. A track hoe here in Canada runs about 1500 bucks a day, and a day's work moves a LOT of earth.

If you are going to build a wall, it needs to be massive. Stone, concrete, brick, block. Ideally such a wall has a hollow core, with the area density different on either side of the core. This reduces coupling between the front wall and the back wall.

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Use a simple laser level from your house to the interstate. If it aligns with fence it's high enough. You can also plant crape myrtles, trees or other vegetation.

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  • Would there be a significant difference if the fence was only just covering visibility vs two feet higher than visibility? Using 1728.org/freqwavf.htm (Air 20 deg C, 800 Hz Frequency) I calculated that the wavelength would be 1.5ft. So maybe 1.5 ft taller than visibility of the overpass?
    – Johnathan Elmore
    Aug 26 '17 at 19:58

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