Trees To Block Off Sound/View Of A Road?
 

I could see the street next to me becoming noisier in the next 5, 10, 15, etc years.

It is not particularly noisy now, but the city is growing and there is room to expand from 2 lanes to 4 - they'd have to eliminate bike lanes and piss off an influential neighborhood, but you never know. . .

So, I was thinking about planting some trees as a sound and visual block now, in case they are needed in 10 years.

I could plant them along the sidewalk grass strip, they'd have to go between and in the shade of a pair of huge, old existing trees. Or I could plant them at the edge of my side yard, which is elevated appx 6' above street level, but also shaded.

Question - how effective are trees, to reduce car noise? What types of trees are most effective? Cypress? Some sort of evergreen? Are deciduous trees are less effective (simply because they're leafless part of the year).

In case it is not obvious, I know zip about trees . . .

Yes, Italian Cypress. Better than a sound wall. They can grow to 40+ ft and extremely dense. Each of ours is about 4ft in diameter. So 3 ft apart should create a solid barrier in the future. Ask your local nursery for recommendations.

Thujas

http://www.fast-growing-trees.com/ThujaGiant.htm

Bamboo works pretty good as well.

Cypress is a messy tree, okay if you are not going to be hanging out anywhere nearby. Oleander is popular, as long as you have no kids or livestock to eat it.

Better check with zoning, planning, road dept. where you live. Many municipalities have regulations on roadside trees...what types can be grown. This is to prevent them becoming a nuisance for various reasons, including roots in sewer lines, lifted roads and sidewalks by roots, etc....

Messy? I don't think so. A few dead inner twigs occasionally nest the base of the trunk and serves as mulch.

http://www.tytyga.com/product/Italian+Cypress+Shrubs+and+Trees

QUOTE: "Question - how effective are trees, to reduce car noise? "
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They aren't. Unless you have the room to plant several acres of them between you and the road in question.

Personally I feel a wall of stone or concrete would be more effective in blocking sound. Then use shrubbery or evergreens to hide. That said, in these parts one can plant right up to the property line as opposed to having an offset for a fence.

Another trick is to mask the sound with a fountain.

Trees, any trees, any amount of trees and type of trees will do nothing for sound decay.

What will affect sound levels (measured)?

1. Square of the distance the sounds fades away.

2. Sight lines (concrete wall close to source or even a tall earth berm).



What will affect perception of sound levels (subjective):

1. Tall trees which block the view and sent/clean or filter the air.

2. Tall fence which gives privacy (that loud sound is on the otherside of the fence, what do I care).


All that said, in my own mind I like to think trees can diffract some sound. All that really means in real life is that the direction of the sound source will play tricks on you, and not much else.

Budget for better windows and insulation if you perceive a problem down the road.

Outdoors? I think you're screwed. Wear earplugs.

Laminated glass, a winner.

Here's a tree wall bordering my yard that absorbs sound. Got some rain and wind so they are little mussed, but they clean up well. The wall next to them is six foot for reference. These are Italian or Mediterranean cypress.

http://forums.pelicanparts.com/uploa...1190668030.jpg

We use berms or a wall to reduce noise when highways get close to homes. Walls are about pretty expensive. Berm takes up more room. Trees may muffle it a bit but wont silence the traffic.

Topographical features work better (berms) but dense vegetation will help somewhat with diffusion.

QUOTE: "Here's a tree wall bordering my yard that absorbs sound."
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That borders a street/highway with moving traffic? Or your neighbors yard?

TEST
1. Get a decibel meter.
2. Take readings as cars, trucks, motorcycles pass on the city street.
3. Plant as many trees as you can.
4. Wait 10-?? years for trees to mature.
5. Take decibel reading.
6. Compare step 2 readings to step 5.

I'll await the results.:)

The experimental methodology is flawed - there's no way to ensure that any gains or losses in dB are due to the vegetation. If traffic density doubles in that 10 years, even a positive effect by vegetation would be shown as a loss. Conversely if the vegetation does nothing and the traffic density decreases in 10 years, you'll show a gain.

Objects do diffuse sound waves and absorb some of their kinetic energy.

You guys that are saying it doesn't matter are quite wrong.

We are in the middle of a huge landscaping project that has required us to take down a swath of ornamental trees and bushes. There is considerably more noise from the street now. We will be replanting a 'green wall' to suck up some of the sound. High quality windows, good insulation and well sealed doors have a significan impact as well.

"Trees, any trees, any amount of trees and type of trees will do nothing for sound decay."

- Wow - I rarely see such completely incorrect statements. I simply cannot understand why people post this stuff when they obviously don't know which end is up.

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

You might try Doug. Fir - they will grow very quickly around here and have rel. dense, persistent leaves (evergreen). You can put something you like better behind them. Plant another row in a few years -- When the originals get too tall, you can cut them and sell them or just rely on the ones behind. You may have some shading issues eventually - if so, cut the tallest ones down.

You can also use slower growing but more ornate trees in the second or 3rd rows you plant.

D Fir is a very fast grwoing tree in the PNW and into SFO as well.

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

You might try Doug. Fir - they will grow very quickly around here and have rel. dense, persistent leaves (evergreen). You can put something you like better behind them. Plant another row in a few years -- When the originals get too tall, you can cut them and sell them or just rely on the ones behind. You may have some shading issues eventually - if so, cut the tallest ones down.

You can also use slower growing but more ornate trees in the second or 3rd rows you plant."
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OK, time to ask JYL for some data. How far is your home from the street/road that is causing the 'problem'.

My point (somewhat tongue in cheek) was; unless he has several hundred feet of space, to plant (as you suggest) row after row of trees and then wait for them to grow and make a difference ... he is better off with suggested 'other' noise abatement methods.

And yes, my 'TEST' was not at all scientific, just an attempt to show the humor of a few trees planted in an attempt to reduce road noise.

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

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.

Trees will work. You just need to plant LOTS of them :cool: 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.

http://forums.pelicanparts.com/uploa...1190760628.jpg

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):

http://forums.pelicanparts.com/uploa...1190760701.jpg

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.

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.

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.

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 ....

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.

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. . .

The Arbor Day Foundation highly recommends trees as noise barriers :cool:

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.