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Do Noise Walls Work?

Posted January 17, 2011 8:30 AM by Steve Melito

Noise walls are expensive and, in some cases, downright ugly. Built an average cost of $1-million (USD) per kilometer, these outdoors barriers are designed to reduce noise levels from roads, rail lines, and airport runways. Often, they also block the line-of–sight between nearby neighborhoods and planes, trains, and automobiles. Although most noise walls are still made of wood, masonry, or metal, some noise barriers are now built from earth or other materials – and colored something other than gray.

In some places, transportation professionals are required to include noise walls in their plans to build or expand roadways, railways, or runways. For example, highway engineers in the United States may be required to estimate traffic noise from a new bridge in a busy urban corridor. But just how accurate are these traffic noise predictions? And how acoustically effective are the noise walls that state, federal, and provincial tax dollars pay for?

According to a technical report from the International Institute of Noise Control Engineering (I-INCE), there is "a strong body of evidence" to support the use noise walls as a means reducing surface transportation noise. The "best description of barrier performance", the report continues, is insertion loss, which the I-INCE defines as "the difference in the noise environment before and after the noise barrier is built". Typically, common values for A-weighted insertion loss range from 5 to 12 dB.

Are noise walls the best way to reduce noise levels?

Source: I-INCE Publication 97-1

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#1

Re: Do Noise Walls Work?

01/17/2011 10:41 PM

I suspect in may cases they work to reflect the noise to some other areas, sometimes you will find yourself many miles from a particular busy road and hear the noise very clearly when there is no or little backgroud noise where you are.

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#2

Re: Do Noise Walls Work?

01/17/2011 11:44 PM

The new patterned concrete barriers that are an amalgam of rubber chips and concrete seem to do an admirable job of attenuating the traffic noise. However these are still only " treating the symptoms " When you ask if it is the best way the answer would obviously be no. The best ways would systematically address the root causes. 1st and best would be mass transit of course. To keep the traffic levels and types we have now would lead us to investigate smoother pavements, lower rolling resistance tires and more aerodynamic vehicles along with better mufflers or electric propulsion systems. Eliminating the noise instead of attenuating it would be the "best" solution.

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#3

Re: Do Noise Walls Work?

01/18/2011 10:22 AM

We had new developments built along an interstate, and after the homes were built and sold, the new home owners united to have the towns pay for sound barriers.

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#4
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Re: Do Noise Walls Work?

01/18/2011 11:31 AM

You are correct. GA. They (or the promoter) got a good deal on cheap land by the highway. They knew that the road was there when they bought. They should be the only ones paying for the walls.

A solution is to use common sense and build the industrial parks and commercial centers by the highway. Have the residential areas farther away. Is that too complicated for your average city planner to understand or is it political pressure from the stupid politicians?

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#7
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Re: Do Noise Walls Work?

01/18/2011 6:32 PM

50 years ago my lawn bowling club was built within 10 metres of a single railway line & the frequency of trains was one every 4 hours.

Evolution is inevitable, there are two lines now & the frequency of electric trains is one every 30 minutes.

The noise is horrific when a train passes & concentration is very difficult.

Economics make a relocation of the greens or a sound wall improbable.

There is a 80metre long row of thick intervening bush about 2 metres wide & high.

I thought an addition of a cheap wall of timber and PVC corrugated sheeting may help to reduce the noise somewhat.

Comments would be appreciated.

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#5

Re: Do Noise Walls Work?

01/18/2011 11:42 AM

Sound walls provide a buffer for the residents of the homes next to the road but will never eliminate sounds. Better than the old chain link fences for sound they also promote a sense of privacy for the highway home owner. As a kid I remember driving by and seeing what the highway home owners were barbecuing.

We live better than half a mile from the highway in a valley surrounded by forest and it just depends on which way the wind blows over the walls before we hear the sounds.

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#6

Re: Do Noise Walls Work?

01/18/2011 1:08 PM

When I bought my house about 10 years ago (some 2 kms from the highway), there was a few hundred feet of forest along the highway. The whole neighborhood was quiet with only birds chirping (winters would be a lot louder since the trees were all bare). Land sold, they stripped the forest for a new commercial center and I could immediately hear the change while drinking a coffee early one morning on the balcony. What a racket!

I think mother nature already provides us with the best (and more esthetically pleasing) sound barrier. Now if we could only stop destroying it only to try and replicate it with concrete....

Done ranting...

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#8
In reply to #6

Re: Do Noise Walls Work?

01/19/2011 6:56 AM

That's the idea. Maybe they could try a row or two of evergreens rather than fencing.

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#9
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Re: Do Noise Walls Work?

01/19/2011 7:24 AM

Indeed, GA, I was going to say trees, but you beat me to it.
There are too many idiots who can't think outside the concrete box.
Trees trees trees trees trees... give 'em a hug, go on you'll feel much better for it
If the planting is done right they can be self sustaining, quick and cheap, a mix of fast and slow growing species, they absorb CO2 as well as noise...make great bows too.
Del

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#10

Re: Do Noise Walls Work?

01/19/2011 11:18 AM

I remember crunching numbers before good computers were available in the early 70s (I was employed as an environmental officer at the time). I was sent on a specific course for such work. This course was intense but in reality I had little to do with barrier projects as post course work. So my knowledge retention on noise today is very poor. As I recall it was tedious work and required many computations for each site. The article is correct as the reduced weighed dbA at a frequency of 500hz is about 10dbA or the equivalent of reducing traffic flow by a factor of 6. The weighted dB is somewhat a problem because the low pitched (frequency) sounds would simply roll over the barrier. The benefit was that the low sounds usually did not interfere with speech so they became acceptable. The idea of natural barriers (trees) were very good. Also reduction of sound is squared for every doubling of distance from a measured site. Some of the ideas of the day were to increase acoustic properties of building along freeways, plant trees, berms, higher barriers, and increased building setbacks.

Higher walls did not attenuate the low frequency rumbles of trucks but did deflect the higher frequency sounds better. If you are in an apartment along a freeway and your balcony is above the barriers, your only reduction from the noise would be distance if you were outside facing the freeway. There are many handbooks available on designing barriers for noise.

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#11

Re: Do Noise Walls Work?

01/19/2011 4:17 PM

The question was "Do Noise Walls Work?", and the answer is: Yes they do, if you set the criteria low enough. And that is what is done. There are complaints, money to study the problem is sought, if it is found, possible solutions are generated, criteria are developed (or found in "accepted" standards), the proposed solutions are evaluated by the criteria developed, and a design is selected. Then money is sought for implementation. If it is found, final design is completed, and the original design adapted to the available funding and the exigencies of site, property ownership, and political conditions.

Yes, leaving a wide buffer with forest cover in place costs less than removing the forest and building a sound wall. It lets the community breathe cleaner air. It cools its environs. It provides wildlife habitat. But it generates no income for its owner, nor tax revenue. In fact, it costs government to patrol it - on foot, and it costs its owner (private or public) to clean it of detritus periodically.

Sound/noise walls are a partial solution to an otherwise insoluble problem which we have created for ourselves out of our desires for convenience, speed, and economic growth. But they do work; not very well, but well enough to justify themselves under the current rules of the game. Trying to identify a single culprit is pointless. The enemy is us, once again.

In case it is not obvious, I hate them too.

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