How Highway Noise Barriers Can Make Traffic Louder - Cheddar Explains 

In Sweden, all noice barriers I see is made out of wood, and shaped in a way to try to catch and trap sound. Where each piece of wall is an S-shape, where I assume they aim to trap sound in the "boxes"

As any City Skylines player will tell you, trees are the best solution to noise pollution. Not only do they have far more surface area to absorb sound over, they also have the added benefit of absorbing some of the pollution from the cars on the road.

Diffusion and absorption are the way. Reflections literally create an echo chamber. Physics are cool

Huh. I was just researching a video about urban noise. This is good timing!

This is exactly what happened by my house. The side closest to the road needs to be made to look like recording studios with sharp pointed angles to break up the soundwaves instead of just flat surfaces for the sound to bounce off of and spread out.

Trees work better.

I grew up near a major hwy, even at 200 feet I could still hear it. Now I need it as whitenoise to sleep. I don’t like a quiet house at night.

So basically, concrete is so convenient that even after it's been proven that it not only doesn't work, but it makes the traffic noise *worse* and more deafening, the state won't do anything because doing so is a pain in the ass. Yeah, sounds about right.

Trees and bushes combined make for the best sound barrier and they have environmental benefits like cleaner air

in the netherlands we build hills out of earth next to highways to have reduced noise whilst it looking better and also working better

Sooo.... what about trees? Plant a good 20-30 ft thick row of trees, make sure they're a fast-growing, dense-foliage species of evergreen. They take care of themselves, they're soft so they absorb the noise, and the dense foliage and 20-30 ft thick row makes sure that there aren't large holes for sound to pass through. Drivers get something green to look at, instead of grey, residents get something green to look at, instead of grey. Road noise isn't refracted over the barrier, it isn't reflected back on cars, and we get a 1st stage filter on all the C02 being produced.

Highway, then train tracks, then thin row of trees. That's what I have to deal with; no concrete noise barrier and apart from when the engine part of the train passes the noise I get from the highway and the train tracks are well within my comfort zone.

typing from nottingham uk. trees and hedges they do exactly what you need them to do, look pretty and reduces noise

Not building interstate highways through residential areas would probably also be a good idea.

I used to own a house a couple homes next to the freeway. Since we were on a hill you could not see it. Pretty everyone that came to my house would ask where is the river ? It sounded like a running river. I am happy I no longer live near the freeway.

The different types of asphalt/"pavement" make a HUGE difference. We have two types here in Germany. If a highway (Autobahn) section needs to be replaced, they use the "new" less noisy type. You will notice the severe change in noise when driving from the old road onto the new one. Its less than half the noise at least, as far as I can tell.

I noticed this in the small town I grew up in. There was a railroad track going through town in a deep trench. When the train would sound it's horn it would be extremely loud and annoying. I always wondered why they didn't just put the train tracks on level ground. Also, the house I live in now has the highway noise problem. We are 150m or 492ft from the highway barrier and the sound is deafening at times. Honks, sirens and street racers can be heard as if they're right outside our house. I hate being outside in the afternoon especially when trying to have a conversation.

In the Netherlands, there are glass barriers at some locations in the city. It's also angled and not 90 degrees. Don't know much about it but it seems very effective. They also use a lot of greenery and it seems to help as well.

For almost 3 1/2 years (Oct. 2017 - Feb. 2021), I lived in a dump of an apartment that was only 400 feet from one of the busiest freeways in the US. No barriers of any sort---not even a skinny hedge---to block the sounds, and the noise level was constant, loud, and hard to bear. My sleep suffered hugely for it. Moved to my current apartment In Feb. of this year; now the same freeway is about half a mile away, and there are numerous business buildings, as well as a small apartment complex of two-story buildings, between it and my place, and these buildings run perpendicular to the freeway, so any sound from there is mostly deflected back to it by those buildings. The only time I really hear it now is when the wind blows from the north---from the direction of the freeway---and it blows the sounds of the freeway between our buildings. It's so rare, it's not a problem, though. Then, only about 1/4 mile behind the apartments, we have a train track on which about six freight trains a day travel; again, though, not much of an issue---none, really---partly because they go through so quickly, and partly because there are a lot of trees and low, one-story buildings between the tracks and this complex. The engineers also don't get crazy with sounding the train's horns, using them appropriately for the 3 or 4 crossings near here, so again, not offensive. It's amazing, though, how moving back off the freeway by half a mile, and having those buildings (and some mature trees, though not more than a dozen) makes such a huge difference in sound. Now it's peaceful, and often downright quiet here, which I'm so very thankful for! My sleep quality has improved so much, I can't even compare it to the other place.

Maybe the ussage of trees will do the same intended purpose but also improving air quality... don't know why it is not used already

"You have become the very thing you swore to destroy."

Noise control: reflection diffusion, diffraction absorption

In portugal they are made of plastic and are usually transparent with bird designs on it

“Depending on distance, noise can reach 70-80 db at 50 feet” nice contradiction on the opening line

The barriers are already there and unlikely to be removed but they can be improved by adding bushes and veiny plants to grow up the wall. This should soften he wall and absorb some of the noise.

The A7 highway in The Netherlands has a wall of dirt retained by steel skeletons with plants growing by side of it as a sound barrier. It truly works as it’s being reflected Bach to the road because of its shape and absorbed by the plants and dirt.

Cheddar always answering the questions in the back of my mind.

In the Netherlands the sound barriers are placed at an angel, so the reflections are directed to the sky. this method is way more expensive since the foundations of the barrier has to be complex, but it's effective

Where i live they use Earth walls they work well and get nice and green over time :)

I've live directly across the street from a freeway exit noise wall. I was there before the wall was built. Its installation has been a game-changer. We can now have a sidewalk conversation. Of high significance is the message a noise wall sends: "This is an area to protect, please respect neighbors with lower speeds, quieter music and less litter." I-5 at Roanoke Street in Seattle -- the busiest stretch of highway in the Pacific Northwest. From experience: I support noise walls.

I’ve seen wood barriers around where I’m from. Not sure if they are any better than concrete. Imagine maybe they absorb more sound. But still. Maybe put some trees there. I get perhaps it’s because the trees will take years to get to a good size. But if they had started back in the 70s it’s would have been effective by now. Probably last longer than a concrete wall. Looks better too for everyone involved.

The highway by my parents got a noise barrier installed... for a cemetery and long stretch of wooded area.

In the UK we texture our barriers and put wooden grids on the top to further diffuse the noise. It works better but I don't know how much better in comparison to earth.

In Sydney they put a lot of plants, trees, and vines on the walls to absorb sound. Also it helps with air pollution.

I studied road noise years ago. What I found was low-frequency sound waves are tall and need a tall wall to stop them. It also helps to have texture on the wall or strategic grooves. The permeable road surface sounds like a good idea as it may help drainage as well.

I live in Finland, and here often I see mounds of ground - looks nicer, more eco-friendly and is a soft material

in the UK I've seen lots of wood fencing, I imagine its a lot cheaper and more absorbing, but also they're not a flat line, so then the sound gets reflected randomly, being quieter

Tunnels and tall walls are amazing, when I go through one with my four cylinder car, it sounds like a screaming v6 😂

Many North Western Europe highways do not have barriers that are perpendicular to the road but instead set at an angle. Also, many are made of more absorbent materials. I would assume that concrete is highly reflective and that the height of the barrier should not be a multiple of the dominant low frequency sound wavelength that tires produce. In particular, these low frequency signals can bend around corners. While they are self-canceling in certain regions they also become amplified in other regions when they collide such as described in the video.

We should build industrial areas around highways instead of residential. Industrial areas can deal with the highway noises, plus it will benefit the trucks that need to get places.

I live near the end of a cul-de-sac, and then there's a wall then the 8-lane interstate. However, the interstate is also in a bit of a valley, which seems to help direct the sound up rather than just over the wall. Inside with windows closed, it's quieter than a desk fan, honestly. Outside or with windows open, it's still much quieter than a conversation.

What's with audio?

In Korea, some of those walls are 5~8m tall and are covered with vines, it will clearly have more efficiency to reduce noise and look better.

interesting, i always thought it was the engine noise, and as electric cars become more common the noise level will just drop.

The most effective noise barriers ever provided are earth and trees. Not only do they properly break up the sound they absorb a lot of it, and they last a hell of a lot longer than concrete while also being much more environmentally friendly. Even if all they do is plant native shrubs along the verges of the highways they'll find they'll have a decent reduction in road noise.

I noticed in Japan their noise walls are curve into the road at the top, which might help lengthen the deep sound shadow behind the wall

I have never in my life seen a sound barrier made of bare concrete. Sound barriers here are usually covered with cement-bonded wood chippings creating a porous surface. They're usually pressed into a corrugated shape to further diffuse and absorb sound. Sound absorbing panels made of wood and glass wool are also common along motorways.

okay but you could also just reduce the amount of vehicles by massively improving public transport especially in large and medium-sized cities, that would already make a big impact, be environmentally friendly and also give people social mobility.

I live in Brisbane, QLD, Australia. I have driven extensively around the eastern mainland between Bundaberg and Melbourne. The vast majority of all noise barriers that I have seen are metal uprights (Stainless steel I might guess) with treated timber slats horizontally between them. Often, there will also be a row of trees on either or both side/s of the barrier as well.

I mean, the whole building huge highways everywhere is an initially attractive, but ultimately terrible and unsustainable idea that the American have been continuing on with regardless. So it seems noise barriers fit quite well with the rest of what you're doing tbh.

If you are going to put up a concrete wall, a wall that is shaped like an egg box and tilted towards the roadway should reduce the noise as the shaped zones will reflect and cancel noise and the tilted wall will direct the residual sound back to the source

Cheddar always interesting. What about growing ivy, or something, up the walls? Or, idk, hedge rows. to help absorb sound.?

I lived about a mile from the interstate. 8/12 months, you couldn't hear anything because the wood was so dense. But in the winter, when the leaves fell, you could hear vehicles far away. It wasn't loud, but it was noticeable late at night. It's kind of odd, being almost on farmland, and hearing a truck engine brake before an exit on a snowy night.

This is why we need underground tunnels and more open space for people and nature

My middle school was about 1km south of the QEW, a highway that has a noise barrier at that section, yet I could still hear the loud drone from it, clear as day

3:10 - 50 ft, 100 ft, 200 ft, then 200 ft again...? I blame the viewers for not supporting Cheddar enough to hire a better editor. ;)

In the Netherlands we have very silent asfalt on our highways. It’s called ZOAB and ik really makes a difference. Also we typically grow plants on our barriers that helps a lot too.

We just need to start reducing our highway needs.

In germany, we either have them in a special diffused shape, or we use dirt mounds overgrown with grass and local plants.

Soil walls seem pretty effective to lower noise pollution from motorway 🛣.

I live in a rural suburb, in a small track of homes, surrounded by grassy dairy land. I am within 1 mile of a four lane state highway, with out a sound wall and I can not hear the highway. However I used to live on one of the dairies. It was three miles away from the highway, without a sound wall, and I could hear the freeway every night.

Always appreciate the metric conversions. Cheers from Canada.

The choice of concrete is surprising - it's much more expensive than pressure-treated plywood, or pine boards - hmmm, maybe the concern is vandals burning it? Here in Queensland the wood is often in panels that are separated by steel - usually a universal-column - a fire wouldn't propagate very fast. The wood is often green [copper napthanate] so the wall 'disappears' behind a few shrubs - and the Main-Roads-department is obsessed about planting shrubs - every shrub you plant eliminates another bit of grass to mow - and if someone crashes off the road shrubs will slow them down before they hit something hard.

As with most Cheddar videos, bumping the speed to 1.25 helps with. The. Slow. Narration. Speed.

The porous asphalt used in Arizona is called asphalt-concrete open graded friction course or rubberized asphalt. It's actually a pretty quiet pavement for the first five years. Then it's not so quiet. Diamond cut concrete seems to be a longer solution but not as quiet.

Physics pretty much disproves their use. My acoustics I professor in college suggested planting trees and installing a fountain in your back yard. Your ears acclimate to the sound and if your eyes see something else that makes constant noise (like said fountain) you can trick your ears into believing the sound is coming from that

Noise barriers are effective if the materials use absorb the sound. Build it just out of concrete will reflect the sound. We learn this in first year city planning.

I thought it was so cars wouldn’t go crashing into houses, stores, etc when there were to be a accident or something

The barriers must be curved on the upper quarter or lean in the direction of the noise source to reflect the road noise back to the traffic. Wooden crash barriers are also helpful for noise reduction.

Wait until you hear that these barriers can bend over the road like in Asia! Then they might work better

In the Netherlands it's common to use earthworks as sound barriers. These are bound to be softer than concrete and thus absorb more of the noise, I also don't see how anything can be more durable than landscape. Keep it covered in grass so it don't erodes and it'll never have to be replaced.

5 mins video in 4 words: concrete hard reflect sound

Makes sense. I grew up in SOCAL next to a major freeway, there was always that constant white noise, but when I visited a friends house who’s backyard was up against the 20’ tall freeway wall, It was noticeably more quiet than my house which was about 6-7 houses away from the freeway.

Awful audio quality, not very informative... Feels like the channel has been letting its quality control slip lately. Still some good stuff, but quite a few wastes of time too.

I just sold my condo where I’m right next to a freeway. So glad to be moving. I can verify many of the effects described in this video.

when you live in a condo and your condo is the noise barrier for the housing area behind

In Phoenix we use rubberized asphalt that is asphalt that has used car tires ground up in it and it makes the road so much quieter for everyone and helps will water drainage when it rains.

I’ve always thought they were there to annoy the passengers views of the scenery, but I later learned it was for lessening noise pollution.

I wonder if we'd be able to fill the barriers with recyclables that don't break down easily, like plastics, to be used as a filler. The junk is put to good use and it makes the walls cheaper.

Or maybe we could just use less cars in general

We live in such a noisy world that it's no wonder people go crazy. There's a story out of Australia where they built a pedestrian bridge over a highway. Not only do the neighbors deal with the highway sound but the way the pedestrian bridge is constructed, it resonates and produces a high pitched hum when it's windy out. And the same thing is happening with the Golden Gate Bridge after a renovation.

please buy a better microphone, your videos are so well edited but the audio really makes them a lot worse

The atmospheric condition which defeats sound barriers is called an inversion, where the temperature rises with height-cool clear nights are ideal for inversions. I live about a mile from the freeway and generally can't hear the noise, but when there is an inversion I can hear the highway noise very clearly. In fact, I can hear trains five miles away easily.

Car tire noise from roads and (and freeway) noise is not much of an issue. It comes out as a hiss sound. However, the #$!@! that insist on making their vehicles' engines as loud as possible and then relish in making that noise - THOSE are a pain, and there are way too many of them. On-ramps are bad, as are intersections for this. Used to be thumping stereos, now it's roaring engines.

Our house was built in the 1930's (About 25 feet from the road) and at the time the road was dirt/gravel and little traffic, had 90% corners so slowed traffic. (We have been here 28 years) The road (Springhill DR/'Springhill Raceway', Albany Oregon, 7.5 miles long and wanders cross country) now has increasingly over the years become a shortcut for commuter traffic, Farm equipment, trucks, log trucks and Semi's because there is a stoplight at the south end end in town and they cannot get on the other east-west highway 20 further west because of increased traffic. Now with the road being pavement and having being built on a poor base it has needed to be torn up and redone for several years. The county's solution was to chip seal (tar and gravel) it multiple times. Well chip sealing a road makes it much louder. Talking to the county, we were told that it would be repaved in 2018. Well here we are in 2021 and all we have gotten is grinding out strips where the road has breached through the pavement and putting in new asphalt (by the county crew, not well trained pavement workers) while they have repaved from milepost 5 into town twice. They also come out after every rain storm and fill in the blowouts on the last 2.5 miles with temp patch. So we can definitely attest to the noise created by different pavement types, potholes, improperly patched roadway, loud muffler cars, certain motorcycles, mud tires on pickups, trucks, log trucks, semi's, farm equipment Etc.

I thought those walls were for safety, to help reduce cars from careening off highways accidentally, as well as preventing pedestrians from wandering onto highways.

Where I was growing up they would plant a whole row of tall pine like trees and I think they do a better job of absorbing and diffusing the noise. Also I think they would absorb some (but only some) of the smokes and fumes as opposed to a concrete barrier.

The solution is to completely enclose the highway or build it underground

Here we use porous concrete lining turned towards the road (could be normal concrete on the outside) and top of barier is curved or bent towards the road. Those porous bariers absorb the sounds and curved/bent part creates better shielding. Plants like vines that are able to grow up the wall can be used too to make it look and function better. It's better than trees because it needs maintanence only as often as repainting the lines or fixing rails so it won't cause too many delays in use.

Plant plants on them. It is cheap, looks good and reduces sound a lot

I always saw those when driving on the highway, but I was thinking that this is for the light from the car to not reach at people houses at night. I learn a new thing today thanks to YT

Depending on the distance you can have x decibels at 15 ft. Nobody else see a problem here 😂?

We live 1.2 miles away from I-64 in St Louis County, Missouri. There are NO barrier walls and we easily hear the highway traffic all night, despite multiple subdivisions and a park between us and the highway.

Just add Stryofoam on the walls

I live near two parallel highways 300m apart; a national artery, and a regional artery, and a railway. They are separated from my residential area by a vlei, and I am put further away by 8 rows of homes. Sounds great, but it's a hill. At night I can hear everything as a constant drone if outside, and trucks using exhaust brakes and drag races penetrate any kind of wall.

@5:08 "Concrete walls have to be replaced every 30 years or so." Really, you seriously think that? LMAO

Sound (and even light in certain cases) can and does bend around barriers and other physical objects, so even a noise barrier could end up bending blocked sound waves towards the houses it's supposed to protect from noise.

just don't build houses around big roads lolololol

I live almost 2 miles away from a freeway with a noise barrier and I still hear a faint roar 24/7. I never really noticed until I visited someone else’s house 45 minutes’ drive away from the city. It was so quiet, I could hear my ears ringing because I wasn’t used to it.

I live near a main road without a noise barrier. This video focused on tire road noise, however that is rarely the problem where I am except for heavy trucks. Overly loud exhaust from cars and trucks and motorcycles are the real problems we face.