Trees To Block Off Sound/View Of A Road?

[David]

It's also my understanding that berms work the best. Maybe a little 2 or 3 foot berm topped by trees or hedges.

[kach22i]

Originally Posted by RWebb

Trees will significantly attenuate sound and this is well published in the scientific literature. How much depends on foliage characteristics.

Show me one, just one source of "scientific literature" which supports your statement.

I'll show you someone trying to sell trees.

Follow the money.

[CurtEgerer]

Trees will work. You just need to plant LOTS of them According to the Fed Hwy Admin you would need to plant a 200 foot deep plot of dense trees to have any real affect. And then it would need to extend well past your property line on both sides - not just directly in front. Even then, I'm skeptical. I used to live on a busy highway and I can guarantee that planting a 50' strip of dense vegetation along the road will do absolutely nothing, other than psychological. You need tall solid mass.



A real sound barrier being built in Lansing MI right now (note that they're cutting through dense woodlands to build this - obviously, the trees did nothing):



You'd be better off installing the best windows and doors you can and adding more insulation to the walls if possible. Then stay inside.

[jyl]

I'm right on the street. It goes: street, grass strip, sidewalk, then my side yard which is about 6' above street level. I could plant in the grass strip, or at the edge of my side yard.

The amount of noise is not large, currently. Most of the day, a car passes every minute - often fewer. At commute hours, there can be 5 cars a minute. I'm thinking ahead to the possibility that the 5/minute pace becomes more common over the years. Any worse than that, and I'd just move.

[David]

On the other hand, after a few weeks, you hardly notice traffic noise. At our last house, we slept within 20 feet of a busy street. The only thing we'd notice were fire trucks. Now we back up to a RR track and now we don't even notice when they blast the horn.

[CurtEgerer]

That's funny. When we finally moved from our house near the highway to our present very quiet location, I couldn't sleep for months. The quiet kept me awake. I'd gotten used to the white noise of the traffic ....

[RWebb]

kach - if you want me to do literature research for you please contact me for a retention agreement. I am, as far as I know, the only research scientist and attorney between Seattle and SFO and my fees reflect that.

[Porsche-O-Phile]

From AIA's "Architectural Graphics Standards", Eighth edition, p. 123:

"Sound Attenuation - Plantings of deciduous and evergreen materials reduce sound more effectively than deciduous plants alone. Planting on earth mounds increases the attenuating effects of the buffer"

And there's a nice simple illustration showing sound refraction by (deciduous) trees. . .

[CurtEgerer]

The Arbor Day Foundation highly recommends trees as noise barriers

And then there are studies based upon science like this from CalTrans:

Traffic Noise Attenuation as a Function of Ground and Vegetation by Rudoff Hendricks (CALTRANS, office of Materials Engineering and Testing, 5900 Folsom Blvd., Sacramento, CA. 95819)(July 1995).[TD100:CA 95-23]

This report concluded that vegetation is usually not an effective highway noise mitigation measure. In this research project, the term "vegetative barriers" refers to shrubs and trees planted in relatively narrow and dense strips along highways for the primary purpose of landscaping. As used in this report, vegetative barriers do not include the specially designed "green" or "living" noise barriers that incorporate vegetation and structural materials for the specific purpose of noise abatement.

Objectives
Measure traffic noise attenuation rates as a function of distance from source, height above ground, and absorptive characteristics of six ground types, ranging from reflective paved surfaces to soft, plowed dirt and ground covers. Measure traffic noise attenuation provided by four species and three heights or thicknesses of vegetation belts alongside highways, such as ivy covered fences, dense oleander and other shrubbery. Establish improved traffic noise attenuation rates and shielding values to be used as inputs for Caltrans noise prediction methods, based on findings in this study. Develop guidelines for use of evergreen vegetation belts (barriers) in Caltrans noise abatement procedures, if effectiveness were proven in this study.

Conclusions
A continuous strip of oleander or equivalent shrubs, at least 2.4 m (8 ft) high and 4.5 to 6 m (15 to 20 ft) wide, planted along the edge of a highway shoulder, provides noise attenuation of 1-3 dBA at distances of up to 15 m (50 ft) from the rear edge of vegetation. A single line of pine trees planted about 7.5 m (25 ft) from the edge of a highway shoulder, 12 m (40 ft) tall, 9 m (30 ft) in diameter, spaced 3-6 m (10-20 ft) apart, low branches intertwined and touching ground, provides noise attenuation of 0-1 dBA at distances of up to 18 m (60 ft) from the rear edge of vegetation.

A combination of oleander, planted 11 m (35 ft) from the edge of a highway shoulder, 2.7 m (9 ft) high and 3 - 4.5 m (10 - 15 ft) wide, and redwood trees, equally spaced at 9 m (30 ft) in the oleander strip, 15 m (50 ft) tall and 6 m (20 ft) in diameter provides noise attenuation of 0 to 1 dBA at distances of up to 21 m (70 ft) from the rear edge of the oleander strip.

Vegetative barriers (as defined in this study) are not an effective highway noise mitigation measure to use on a routine basis. In some borderline cases (to mitigate or not mitigate), thick oleander (at least 4.5-6 m, or 15 - 20 ft wide and 3 m, or 10 ft high) may have some value by avoiding conventional noise barrier construction, if adequate right-of-way is available.

Trimming or removal of shrubs and trees along highways by maintenance or construction does not cause perceptible noise level increases to nearby residences. However, the sudden visibility of highway traffic previously shielded visually by the vegetation, and the possibility of a shift in sound frequencies, may bring on a renewed awareness of the presence of noise sources. This may result in additional noise complaints.