Traffic noise distances

How far can you hear traffic?

My wife has an online knitting friend who used to rent an old farmhouse in the boonies and when we visited I noticed that I couldn't hear anything but the sounds of the fields. It was wonderful. So I was looking forward to that when we were going to move to "the country". Sadly, we failed to actualize that particular aspect. We live 1/2 mile south of a well-used state highway. I can almost always hear traffic from that road during the day. I get up at 0300 and the traffic at that time is quite sporadic so I also know what it sounds like when that road is silent. At those times, I can hear the interstate which is through about 3.5 miles of woods, as the crow files. The interstate is quiet -- a murmur even, but constant. Having had this experience, it seems like what I have is the most noise I could stand and I wish I'd bought somewhere more remote.

But how remote do you have to be in order to get the noise profile I'd like?

I think it depends. Highway noise, as you've noticed, can carry in strange ways, especially if that highway is near a grade, has a lot of heavy cargo or is a nice ride for motorcyclists.

Even remote-remote can be weird. I've mentioned elsewhere that during college I worked a summer at an FFA Fresh Air Fund camp waaaaaay out in the wilds of upstate NY (between a State Forest, a Wilderness, and a Wild Forest... the land of deer camps, bears and not much else).
A good half hour's drive to a paved road, an hour to a town where I could put my paycheck into the mail to my bank. I ran the horseback riding program and the first thing they told me when I arrived was "it takes an hour by helicopter to medivac anyone who gets hurt to the nearest hospital so don't take risks!" No pressure!

It was idyllic most of the time. But it was 40-odd miles from Fort Drum, and when they decided to play with explosives or do maneuvers with jets out at the fort, nobody could sleep and the horses would get upset. So maybe not just the highways but also the skyways are worth looking at.

Besides highway noise as Tereza suggests there are a lot of other factors.

Some could be road surface, such as gravel or pavement, heavy vehicle engines (big trucks), exhaust systems, even the high speed of traffic, all can create a continuous roar.

I am about 1/2 mile off a caliche (dirt) road and I never hear traffic.

When we lived in Dallas, I could hear my husbands truck when he was several blocks away (at night when it was quiet).

My grandparents bought a house on the main road.  Distance is difficult when one is a kid.  3.5 to 4 driveway width distance from heavy traffic

The developer made a sideways driveway parallel to the road for about 5 houses, then between that and the road, built a berm and massive hedge. You wouldn't know there was a main road there.

In Tokyo, I visited a garden.  Tokyo is LOUD.  But as soon as I entered the garden, all the noise stopped.  Completely. No traffic, no nothing.   It was like the scary feeling of being in the forest and suddenly the birds are quiet.

Where I live now, we are so far away from the road.  We could probably fit 6 suburban lots between us and the road.  I'm sitting here with the traffic so loud it's like sitting on the road.  Although, with trees, we've managed to make some quiet spots, it's still a work in progress. I suspect land is better at reducing traffic than trees.

Although, I heard there is a document out there that lists trees by species and traffic noise canceling rating.  I've never found it.

I once looked at a house about a half mile from the Interstate, and I too could hear the background noise as traffic went by. In that case it wasn't too bad. I suspect the more trees, shrubs, berms, and rock walls you have in the way... the less noise you will hear.

r ransom wrote:... between that and the road, built a berm and massive hedge. You wouldn't know there was a main road there.

The shape of the berm matters too. The hedge breaks up the noise, but a berm absorbs and deflects it. Mass counts where noise is concerned. Christopher's post immediately had me thinking 7ft tall hugels!

and wrote:

In Tokyo, I visited a garden.  Tokyo is LOUD.  But as soon as I entered the garden, all the noise stopped.  Completely. No traffic, no nothing.   It was like the scary feeling of being in the forest and suddenly the birds are quiet.

The Japanese are amazing. I wonder if you visited the same place today, would you be able to spot the techniques they'd used to accomplish it. I would hope it was ancient, well used techniques, and not white noise generators!

The lay of the land, the wind direction and a person's hearing profile are all factors. Hubby insists he can't hear the ferry horns from our property, but I certainly can. They aren't loud enough or frequent enough to be a bother. Noise is a pollutant just like smoke, light, and toxic gick, and there are many permaculture ways to reduce their impact, but sometimes, we need good government to step in and build berms with shrubs and trees to help reduce all those things for people's health and safety particularly when roads are involved.

I live about 2 miles, as the crow flies, from 2 state highways.  At night, especially in 5he winter, I can pick up highway noise from semis.   I live maybe 10 miles from an interstate…no noise from that. In both cases, there are a significant number of trees between the roads and my property.

In Minnesota, I was maybe 3+ miles from 371. I never picked up noice from that highway….even in winter.

Is there space for a line of evergreens between you and the road?

My grandma used to live a bit above and next to a heavily used highway. The line of white pines between her and it would muddle the traffic sounds. If I closed my eyes I could imagine I was at the beach hearing the ocean.

Didn't do much for sirens or horns though!

Great question, but it depends mightily on elevation, ground cover, and even weather conditions.


Growing up, there was an interstate about 4 miles from my house.  Normally, there was no indication it was there, not a simple peep. And though it could never be seen, there are times when it hummed.  Strangely, the only time I ever remember it being audible was when the sky was overcast.


I wish I could give a more specific answer.



Eric

Eric Hanson wrote:...  Strangely, the only time I ever remember it being audible was when the sky was overcast.

I don't think that's strange at all - clouds can reflect light. I suspect they can reflect sound to some degree also?

OK, a quick bit of research implied that it isn't actually the clouds, but different layers of air at different temperatures slowing, speeding or focusing the sound. The clouds tend to form at different levels and are definitely affected by temperature.

Do we have any physicists out there who could explain this better? Is it actually a thing that works? I recall from my son's music classes that low notes travel further than high notes (which is also why fog horns are the tone they are.)

Jay,

It doesn’t surprise me that the sound reflects from a boundary layer.  It might be a temperature inversion.

Normally, as one goes up, temperature goes down, but under the right circumstances going up can actually increase temperature.  It takes VERY stable air.  This effect can only happen so far from the surface.

When this happens far enough up, there is a little density layer that forms and the transition point is surprisingly narrow.  

So as sound rises, it does indeed reflect back down, an effect that is best observed some distance (miles) from the source.

Thanks for reminding me about the why to this question!


Eric

Oh, the overcast—-


Those clouds were probably sitting just above the boundary layer.



Eric.

Jay Angler wrote:

Eric Hanson wrote:...  Strangely, the only time I ever remember it being audible was when the sky was overcast.

I don't think that's strange at all - clouds can reflect light. I suspect they can reflect sound to some degree also?

OK, a quick bit of research implied that it isn't actually the clouds, but different layers of air at different temperatures slowing, speeding or focusing the sound. The clouds tend to form at different levels and are definitely affected by temperature.

Do we have any physicists out there who could explain this better? Is it actually a thing that works? I recall from my son's music classes that low notes travel further than high notes (which is also why fog horns are the tone they are.)

Clouds are often indicators of air layers that can reflect, refract, and focus sound -- especially low frequencies -- over surprisingly long distances. There is a large wind farm on the ridgeline close to where I live. The nearest turbines are only 2 km line of sight and there are more than 50 of them. When the wind is strong from the southeast a curved shear zone sometimes develops (basically a Nor'west_arch but from the opposite direction), and this acts sort of like one of those parabolic reflectors that you can use to eavesdrop on a conversation or listen for enemy aircraft. This produces an interference pattern at really low frequencies, so that I can go out in the paddock and, if I stand in certain spots, the sensation is pretty intense. It's felt rather than heard but it's a whole-body sensation, with period of about one WHUMP every 1.5 seconds. If I move just a couple of metres in any direction, it goes silent, but by shifting positions systematically I can pick it up again in many places, sort of in a checkerboard array.

I'm lucky in that it doesn't seem to appear inside the house, but have neighbours nearby who have a major issue at times.

This issue becomes even more important if you need to have windows open to get the cool night air in. I certainly notice a difference. Window glass may not be the best for blocking sound, but it is better than nothing!

#2 Son is thinking of buying a house where traffic noise is likely to be an issue. They are loosing their rental and this is the best they've found that's even remotely in their price range. I am already thinking about what trees/vines etc we can plant to deflect the noise. I will have slopes to concern myself with also. A 7 ft high hugel isn't going to help much if it's more than 7 ft down the slope from their windows!

I wonder if a zigzag hugel would bounce the sound back and forth and absorb it?

There's quite a bit of research on this topic in the published literature. I was looking into it some years back when planting a windbreak that also needed to dampen road noise. I settled on conifers (~10 db reduction) followed by a 15-20' gap, then a dense Fedge (food/hedg) on contour. I found wind direction had a very significant effect. If I was house hunting, I'd want to take into consideration prevailing wind direction and not choose a place downwind from highways (not only for noise reasons).

The investigation of noise attenuation by plants and the corresponding noise-reducing spectrum
by Fan Yang|2010

Effect of roadside vegetation on reduction of traffic noise levels
by Upul Sonnadara

An Investigation of the Noise Absorption Potential of a Six Selected Grass Species
by Nalin Dhanushka Amar...

Investigation of the Effects of Leaves, Branches and Canopies of Trees on Noise Pollution Reduction
by Kobra Maleki|2011

Plants and environmental noise barriers
by Benz Kotzen|2002

Quantitative analysis of sound absorption properties of plants in indoor environment for enabling sustainable practices
by Bimal Roy|2019

The effects of vegetation on road traffic noise
by Rob Bullen|2014

Acoustic properties of low growing plants
by Kirill Horoshenkov +1 more|2013

Influence of urban trees on noise levels in a central Chilean city
by Exequiel Plaza Tauca... +1 more|2019

Influence of urban trees on noise levels in a central Chilean city - Influencia del arbolado urbano sobre los niveles de ruido en una ciudad de Chile central
by Exequiel Plaza|2019

Determination of roadside noise reduction effectiveness of Pinus sylvestris L. and Populus nigra L. in Erzurum, Turkey
by Çoban Yıldızı|2007

Urban cities and road traffic noise: Reduction through vegetation
by Subhadip Ghosh|2017

A review of natural means for noise abatement
by Keith Attenborough|2019

Effect of roadside vegetation on the reduction of traffic noise levels
by channa kalansuriya

A study of the spectral characteristics of traffic noise attenuation by vegetation belts in Delhi
by Vinod Jain|2006

The effects of vegetation on the perception of traffic noise
by Greg Watts|1999

Studies on Foliar Sound Absorption Capacities of Some Urban Trees by Impedance Tube Method
by nitesh joshi +1 more

Noise attenuation provided by hedges
by Giancarlo Imperi|2019

Use of green vegetable barriers as environmental noise attenuators: a case study in Irati, Parana
by Jhenifer Spliethoff|2024

...and this gem and favorite (abstract attached):

An Assessment of Psychological Noise Reduction by Landscape Plants
Fan Yang 1, Zhi Yi Bao 2,*, Zhu Jun Zhu |2011

Of course, the OP was about traffic noise….which I find annoying.  Oddly, I find railroad noise relaxing.  I used to live by a rail yard and enjoyed listening to the noise.

Christopher Weeks wrote:How far can you hear traffic?

My wife has an online knitting friend who used to rent an old farmhouse in the boonies and when we visited I noticed that I couldn't hear anything but the sounds of the fields.

But how remote do you have to be in order to get the noise profile I'd like?

To block sound from getting to your ears you need to bounce it away, or absorb it some how. Sound that has a direct line at you can and will travel far. Long needle pine trees are great for minimizing noise. They keep there foliage year round and make gentle whoosh noise in the wind. Another option is a day on a Doser/excavation.  Make a mini mountain range between you and the road, heck you could make one of those sloped hill gardens Paul seems to like.

r ransom wrote: My grandparents bought a house on the main road.  Distance is difficult when one is a kid.  3.5 to 4 driveway width distance from heavy traffic

The developer made a sideways driveway parallel to the road for about 5 houses, then between that and the road, built a berm and massive hedge. You wouldn't know there was a main road there.

In Tokyo, I visited a garden.  Tokyo is LOUD.  But as soon as I entered the garden, all the noise stopped.  Completely. No traffic, no nothing.   It was like the scary feeling of being in the forest and suddenly the birds are quiet.  

That is fascinating re grandparents!
I’d love to know exactly how this was set up and hedge/tree species etc!!

A book could be written very profitably about those kinds of solutions, in my opinion!

I’d also love to know how the Tokyo garden achieved this!
This kind of info could make many of our living experiences in this world SO much better!

Please do elaborate if you have more info🙏

Agreed about the train noise—if distant.

Under the right conditions I can hear the train which is miles from us at the closest point—and I can hear it from miles down the track to miles up, fading away.

Reminds me of a Paul Simon song “Train in the Distance.”

Eric

That's interesting. There's a quite-active railway that runs along the nearby highway and I mostly like that source of noise. I think because it's so intermittent. The trains run 24/7 but maybe only 4-5 per day. (There's also a small airport and small-craft flight school about five miles away so we get Cesnas and whatever overhead quite often, and they don't bother me either.)

Also, I thought a map might help. It's a little hard to imagine that I can plant a row of trees or erect an 8' berm to combat this. Probably a wall around the house and garden would do it but that's beyond my budget.

Any chance that Central Hall Road is funneling the sound down to your house?

I tried very hard to convince Hubby that Penny Lane should have some curves to both break up the wind and the noise, but alas, he's one of those "straight and narrow" types. Luckily we do have a dirt berm between the lane and the noisy road.

Yeah, for sure. It often doesn't sound like it -- I walk the other direction down Central Hall every morning, parallel to the highway, and it seems like I can tell that a car's noise is coming from off the east or west, or when it's about due north of me, but I don't have any way to know how accurate I am and noise is sometimes tricksy. I think, at least for this topography and ecology, I just needed to be another half mile from the road because it's much quieter in a nearby similar place that's one "block" farther south.

I was sort of hoping that other people who had looked for land would have been more cognizant of this issue while shopping and had figures like, "I really needed to be two miles from a busy highway before I was satisfied" or whatever. But ultimately, I guess it doesn't matter. I think I'm done moving unless things go much further sideways in the wider world.

J. Syme wrote:To block sound from getting to your ears you need to bounce it away, or absorb it some how. Sound that has a direct line at you can and will travel far. Long needle pine trees are great for minimizing noise. They keep there foliage year round and make gentle whoosh noise in the wind.

Do you think pine needles would be better than other conifer foliage? My property is full of Red Pines, but they are close to 40 years old and have no needles below like 20 ft so no help for close by traffic. There are firs, spruce, and pine saplings springing up randomly, but I planted a sight/sound barrier of White Cedar (arborvitae) in two staggered rows where there was a direct LOS to the road. I figured the density of their foliage would be optimal. Unfortunately I didn't fence them off from the deer...

Coydon Wallham wrote:

J. Syme wrote:To block sound from getting to your ears you need to bounce it away, or absorb it some how. Sound that has a direct line at you can and will travel far. Long needle pine trees are great for minimizing noise. They keep there foliage year round and make gentle whoosh noise in the wind.

Do you think pine needles would be better than other conifer foliage? My property is full of Red Pines, but they are close to 40 years old and have no needles below like 20 ft so no help for close by traffic. There are firs, spruce, and pine saplings springing up randomly, but I planted a sight/sound barrier of White Cedar (arborvitae) in two staggered rows where there was a direct LOS to the road. I figured the density of their foliage would be optimal. Unfortunately I didn't fence them off from the deer...

i like the white noise, sound of the long needle pines better than the shorter ones, my personal preference. the longer softer needles seem to have a denser foliage. What you need is a variety of sizes and shapes in the woods to break the noise into tiny scattered bits. might be worth it to mix in some ground cover and some new pines in with the 40 yrs old's.

Jay Angler wrote:Any chance that Central Hall Road is funneling the sound down to your house?

This was the case at my parents place. They were at a higher elevation than the interstate and a good distance from it but there was a fairly straight powerline cut that I think brought the noise in or contributed to it. It was a beautiful 20 acres but the noise always really bothered me because you could not see a neighbor or the road for that matter but the noise was always there.

Low frequency sounds travel far, subsonic sounds included. That's a major reason that people living in the vicinity of industrial wind turbines complain, because sound too low in frequency to be heard can still be sensed.
As for relying on remoteness for avoiding road noise, I recall decades ago visiting a remote property on a mountain in the interior of British Columbia and noticing sound from a highway miles away in the valley below, despite the intervening forest.

Hello, a long summer outdoors constantly.  The house losses itself and we become the  garden, orchard, and forest, yet the drone of autos.  I’m in Christopher’s boat with a HWY about 2 miles away and elevated across a valley.  My architect uncle in the mountains of CA a long time ago suggested Dawn and Coastal Redwoods.  Curious much of Northern North America, Greenland, was covered in Dawn Redwood, Metasequoia during the Mesozoic and Cenasoic.  Not a short term fix but a complete wall maybe 70-80’’ in my lifetime, and taller for my son.  Planted on a Hugelkultur line of dead Doug Fir buried at 4-6’  to the surface and a second planted group 20’ in front of Taxus Baccata Yew’s, and Chilopsis Linearis Dessert Willow, all in a 4’ deep sub swale just a double dozer wide  road.  With a 2’ high 2’ wide burm down center.   Channels to prevent heavy precipitation runoff which may occur this year.  The Redwoods can be sheered when young to gain density, not too hard.  This doubles as a fire line in about 15-20 years.  I can wait for retirement, and I guess peace and quiet.  Cheers.  

Jay Angler wrote:
OK, a quick bit of research implied that it isn't actually the clouds, but different layers of air at different temperatures slowing, speeding or focusing the sound. The clouds tend to form at different levels and are definitely affected by temperature.

Do we have any physicists out there)

My son and I bantered all summer about the “liquid atmosphere” , of Earth 🌎.   I pose that we are all vertically swimming through life.  He counters that he can’t hear me sometimes because his ears are clogged with air/water.  He did ask if clouds makes the traffic sounds louder.  Yes, clouds are a visual mark of temp change in atmosphere, and denser atmosphere reflects more sound wave.  We tested this with temperature, day/night, clouds and no clouds, used a small pocket laser to bounce off the clouds back to photomultiplier hooked to an EyePad.  Star gazing can be tough here in summer, gotta have a backup plan.  Eclipse last week, had em bouncing around for hours:).  Cheers