Question
I need help on fencing .I have a large corner lot in a small NJ town and one side borders a 2 lane road that has become very busy over the years. I have been noticing increasing incident of vibration through the house from large ,fast vehicles. My house sits slightly below road level .I wanted to know if either a dense privacy border of evergreens or 6-8 foot privacy fencing would stop the vibration if installed at the road side in question?

Answer
Hello,

I would suggest some type of acoustic wall. The wall can be constructed of concrete,masonry or wood. The most effective would be concrete filled with solid foam insulation. Locate the wall as close as possible to the noise source and make it high as possible.

A concrete wall would consist of a series of horizontal concrete boards layed into slots in concrete posts,the space between the outside and inside concrete boards being filled with solid foam insulation. The structure must continue to the ground since noise will get through any gaps at ground level.

An ordinary concrete block,stone or brick wall will also have some sound deadening effect. A concrete block wall filled with solid foam in the openings in the individual blocks would be much more effective.

The comparitively least effective sound barrier would be a wooden timber fence. This type of fence consists of heavy timbers layed horizontally between timber supports. An ordinary wooden fence would not be very effective since it is too thin and sound would transmit through any gaps in the fence.

Another type of wooden fence could be made of exterior plywood panels with solid foam insulation sandwiched between. An exterior plywood fence may have a shorter lifespan than other wood fence types. The plywood must be kept coated.

It is important to seal the tops of all foam filled fences to keep water out. Build the fence as high and as long as possible. Most likely the fence will have to be constructed over the legal fence height for your area and you may need to apply for a variance from your zoning board.

Plants may also be helpful in deadening sound. Follow these guidelines:

Place the noise buffer as close to the noise source as possible.

Plant trees and shrubs as close together as possible.

A diversity of tree and/or shrub species within the buffer may further reduce noise.

Foliage in the buffer should form a continuous wall from the ground up. Use shrubs under trees to achieve this effect.

Use dense foliage plants.

Use evergreen species for year round protection.

Make the buffer as tall as possible.

Make the buffer as wide as possible.

Make the buffer twice as long as the distance of the protected zone to prevent noise from getting in from the sides.

The fact that your property sits lower than the road may be magnifying the noise and vibrations somewhat. Consider using earth berms with the plantings.

All noise will not be eliminated. A planting of 18 feet wide can only reduce noise by about 1 to 3 decibels. It would take a planting 50 feet wide to get a reduction of 10 decibels.  The buffer must extend as much as possible over the point at which you are experiencing the noise and should extend over the noise source. This creates the refraction angle.  

Vibration from traffic that is transmitted through the ground is a bit different than noise transmitted through the air.  Landscape elements for aerial noise control may still have an effect on these vibrations,particularly ground level elements such as ground cover,shrubs,low growing vegetation,berms and soil. Loam and sandy soils absorb noise energy. Ground vibrations are transmitted well through concrete and masonry.
Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.mahdrafting.com
Email: [email protected]

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