Good Fences

An obvious solution to the traffic-noise problem at the Carlisle house would be a high wall to block it out. A barrier fence might also be an effective way to reduce noise, but only if the structure is solid enough and thick enough to shut out the sound waves. As a general rule, the more solid the fence or wall, the quieter it will be, because sound waves are reflected by dense objects. The sheer mass of masonry walls—stone, brick, stucco-covered concrete — make them the best for blocking sound. Next best, and more practical for most homeowners, would be any solid stockade or board fence.

But the material is not as significant as the construction. The fence should have no gaps because sound waves, like liquid, will always take the path of least resistance and flow through any holes. A fence that does not reach to the ground will allow the sound of passing car tires to go right under.

Likewise, a low fence will allow more sound waves to flow over the top. "That's the weakest link in any fence," says Wood, who applies a "line-of-sight" rule: If you can see the source of the noise, you'll be able to hear it. Even a very high fence—say 8 or 10 feet—will not provide much sound reduction for an elevated deck or balcony on the other side. Wood suggests simply building as solid a fence as possible, as high and long as local regulations and practicality allow while still being aesthetically pleasing. One way to fill in the gaps along the bottom is to stack pressure-treated timbers on the ground, running them right up to the fence sections.

An 8-foot-high solid fence or wall might knock 6 to 10 decibels off traffic and other ambient noise, which typically measures 60 to 70 decibels—about equal to the noise an older dishwasher makes. That might not seem like much, but the decibel scale is logarithmic. To the human ear, a 10-decibel drop seems like half as much noise — in this case, from an old dishwasher to a refrigerator's hum.

At Carlisle, unfortunately, an 8-to 10-foot fence or wall isn't a possibility. The house sits on a corner lot, and like many municipalities, the town restricts fences and walls that could block views at traffic intersections. Plus, such a big barrier would detract from the historic farmhouse's curb appeal.

So instead, landscape designer Stephanie Hubbard has called for a traditional 2 1/2-foot-high, dry-laid stone wall along the front of the property. Though traffic noise can still spill over the low structure, the wall's mass will help deaden the sound of tires on the road. And since it will be close to the source of the noise, it can bounce the sound waves away before they head toward the house. Equally important is the character the wall adds to the front yard. "You have a nice feeling of enclosure," says TOH landscape contractor Roger Cook, who brought in masons from O'Hara & Company in nearby Ashland to build the stone structure. "And it looks like it's been there forever."

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