3 Ways To Reduce Road Noise In Your Backyard

Reduce Backyard Traffic Noise

The winding two-lane road in front of This Old House’s TV project house in Carlisle, Massachusetts, is hardly a superhighway, but it is a well-traveled commuter street. Fortunately, better insulation and sealing have made the renovated 1849 farmstead quieter on the inside. But the lawn and garden outside the house are still vulnerable to noise, from the hum of car tires on the road to the buzz of the neighbors’ power mowers and trimmers. For advice on how to reduce road noise in the landscape, This Old House turned to Eric Wood, an acoustical engineer from Acentech, a noise-reduction consulting firm in Boston. “As the population continues to grow, it is reasonable to expect noise pollution to increase, too,” says Wood. But, he adds, we shouldn’t compromise our quality of life and just try to live with it. Hundreds of studies document the adverse effects of noise, from hearing loss caused by extremely loud sounds to generalized anxiety to sleeplessness. Here, Wood provides a closer look at the most common outdoor noise reduction solutions and offers a rundown of what works best.

1. Put in a Noise Reduction Fence

An obvious outdoor noise reduction 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 road noise, but only if the structure is solid enough and thick enough to shut out the sound waves.

What Materials Will Block Sound?

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.

Construction Tips

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.

Will a High Fence Reduce Traffic Noise?

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.

Consider the Character a Fence Can Add

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.”

2. Put in a Fountain to Drown Out the Noise

Hubbard considered another tactic for dealing with noise that reached the front yard of the house: a fountain fashioned from a rustic granite watering trough and a copper spigot. Running water has long been employed to “drown out” extraneous noise and create a sense of serenity — picture the fountains in medieval cloisters or Japanese gardens.

Create a White Noise Effect with Water

Gurgling water creates a continuous sound that is in the same frequency range as other less desirable sounds, such as lawn mowers, air conditioners, and people talking, but because the fountain is nearby, its sound dominates. Today, we call this “white noise.” To be most effective at masking noise, fountains need to be close to the listener — right next to your outdoor area or up against the house. But they don’t need to be elaborate or expensive. “Fountains are pretty simple,” says Roger. “They can be any vessel that holds water — a stone birdbath, a copper tub, an urn — fitted with a recirculation pump.”

Consider the Seasons in Your Location

But fountains are generally seasonal, often connected to a home’s water supply or irrigation system and shut off at summer’s end. And they can’t camouflage sharp, loud sounds like horns or alarms. In the end, the TOH team decided not to install a fountain at Carlisle. The expense and trouble wasn’t worth the benefit of masking noise near the front door, since most of the outdoor seating and entertaining areas are out back.

3. Alter Sound Perception in Our Brains

Along the road in front of the Carlisle house, young disease-resistant elm trees will sit where a couple of older trees had once flourished but had fallen prey to disease in the last century. In the backyard, multistemmed Heritage river birch will replace old, dying hemlocks along the property line, and also in clusters at the outer edges of the yard to buffer it from some of the noise filtering in from the adjacent streets.

In Reality, Trees Don’t Help Reduce Road Noise

Many homeowners consider using plantings like these to block noise from their property, but in fact, greenery has very little effect on noise levels (though rustling leaves can be another source of white noise). The problem is those persistent sound waves, which sneak through the tiniest openings. You’d need a tree swath at least 50 feet deep to get good sound absorption.

But, They Create an “Out of Sight, Out of Mind” Effect on Our Brains

But because sound perception is highly subjective, sometimes our brains can be tricked. The field of “psycho-acoustics” is a recent area of study — though its effects have been observed for many centuries. Four hundred years ago, when European church organists couldn’t reach all the right pedals, they realized they could play a combination of notes that made people think they were hearing a much lower note. Today, some small speakers digitally enhance similar frequencies to create a “phantom bass” effect, making these same components sound like much larger models. Psycho-acoustics also connects aural and visual stimuli. “Certainly out of sight is out of mind,” says engineer Jim Barnes, who works with Wood at Acentech. That’s why plantings create a perceived reduction in noise, even if a decibel meter says otherwise. “As an engineer, I do like to quantify,” says Barnes. “But if people say ‘Yeah, it’s much quieter,’ I take them at their word.”

Consider the Comfort and Aesthetic Appeal

Roger Cook sees it all the time. “Greenscaping that blocks the view of the noise’s source will always make a property more comfortable,” he says. “Even a nice lawn will make you feel farther from the road.” When designing landscapes for acoustic comfort, Hubbard suggests including evergreens for their year-round leaf structure. Among her favorites are Hetz wintergreen arborvitae, a narrow tree good for small spaces; Colorado spruce; and Hinoki cypress. Such greenery can also soften the monolithic look of a noise-blocking fence. “Plantings create some visual interest and break up the hard line,” says Hubbard. Along the wall at Carlisle, hydrangeas, lilacs, and spirea will accent the stone with seasonal flowers and foliage, while a boxwood hedge that will grow to 6 feet will increase the sense of separation from the road. But it’s the backyard that will provide the most tranquil retreat. There the grounds are inherently quieter, shielded from the main road by an acoustic barrier that’s better than any fence or fountain: the newly restored house itself.

Where to Find It

Architect: Jeremiah EckJeremiah Eck ArchitectsBoston, MA617-367-9696www.jearch.com Landscape architecture: Stephanie HubbardHalvorson Design PartnershipBoston, MA617-536-0380www.halvorsondesign.com Noise-reduction consultants: AcentechCambridge, MA617-499-8000www.acentech.com Landscape contractor: Roger CookK & R Tree and LandscapeBurlington, MA781-272-6104 Dry-set stone wall contractor: O’hara & CompanyAshland, MA508-881-6851