I was able to read this entire article despite its pay wall by screenshotting the article before the pay wall came up. I had to reload the page, screenshot several times, and time it right but I was able to read the whole article.
This was a key element for me in overcoming my insomnia, I used to stay awake at night because it was finally quiet enough that I could concentrate. After identifying that as a key part of the problem noise reduction became a focal point. It has created a new problem: the headphones are so good at this that it is very easy to creep up on me and scare the bejezus out of me when I don't receive any other clue such as a changing shadow or something like that. I'll have to figure out some kind of early warning system for approaching people.
Whoever cracks this particular nut without headphones and manages to create a bubble of 2 cubic meters or so that is silent from outside interference will make a lot of money. The article lists one entrant that seems to be a move in the right direction but it does not look like that particular version will be ready for prime time in the near future.
My 'ideal' soundsucker (sonic black hole) is a ceiling mounted device that projects a cone of silence. One possible way in which it could work is by using a phased array of speakers to 'fake' a larger one. But that ideal will likely never be reached due to limitations in physics, imagine the problem as applied to a wavy surface of water: create a wave pattern that cancels out the wavy surface in one circular area without touching the water directly.
Edit: Another - unexpected - benefit is that all the fan noise and other ambient noise in the room I'm in (which I normally don't even notice) also drops by a very large factor with NC enabled.
TBF It’s not even the same company. Part of the same group, but the entertainment companies are separated from music hardware, have their own heads, their own deals etc.
It’s like boycotting Vox media because of Comcast. It follows a logic, but it feels peculiar.
On your general point, totally agree. There was a company touting to “design” everyday noise by sticking a small module we’d keep in our ear canal, the company seems to have disappeared but I was so sold on the idea. Almost permanent noise reduction, or filtering for nearby voices only would be the dream setup.
Same here, particularly during a time when I was living in a noisy apartment building. It was particularly difficult for me as I didn't to take sleeping pills since I'm a bit against those things.
>Whoever cracks this particular nut without headphones and manages to create a bubble of 2 cubic meters or so that is silent from outside interference will make a lot of money.
One of the first things when I got myself an RTX 2080, was learning how to use the ray tracing APIs to develop an idea similar to what you mention. I was using the rays to model the wavefront of an arbitrary source of sound, and then, given a 3D scene of a "room" or whatever, visualize how this wave was traveling through the space and reflecting over surfaces with different parameters.
The point of this was to see if you could find/predict the spots in a room/house/building where noise is naturally damped. The visualization was very nice to look at as I modeled the wavefront as if it had an exaggerated effect over the diffraction of light on the air. I cannot find it now, but there used to be a 2000s or so tv ad for the Beolab 5 which looked very similar in essence, maybe also a bit like schlieren photography [1].
[1] https://ntts-prod.s3.amazonaws.com/t2p/prod/t2media/tops/img...
I love the hacker ethos here on HN. Most places, we would here about how high an fps a person obtained on their favorite game with the settings cranked up. Here on HN, we hear about using the ray tracing api to model sound. It is stuff like this that keeps me coming back: hearing how people are using tech in new, really cool ways!
Poking around I couldn't find them, but there are rather a lot of tiny fish-eye mirrors being sold to affix to the top or corner of a car rear view mirror (so-called blindspot mirrors). Those should be in roughly the correct size classification.
You can tell roughly how far away a sound source is by measuring the curvature of the wavefront, since sound radiates out in a sphere. The farther away you are, the lower the parallax between two sensors.
If you have sensors with 20 cm separation (each ear) then you would need a minimum sample rate of 34.3 kHz to easily correlate sounds within 2 m. With 5 cm separation (to discriminate sounds coming from your sides), you'd need 550 kHz.
Since sound waves are ~10-10,000x lower frequency than that, you need to be able to measure pressure very precisely to distinguish two waves. Rough rule of thumb is 10x, so you'd need up to 1/50,000 precision microphones, or 16 bit. Thats an absolute minimum and you'd probably want ~20 bits.
You might need a DSP and this trick works much better with some high range microphones (electrets are maybe sufficient), but all of that is well within the range of possibility... so I'm kind of surprised nobody has done this yet. I might take a shot at it.
The tricky part is the noise floor, which is only 10-1000x (in terms of voltage from the microphone) below the things youre trying to measure. That means youve got to gather dozens to thousands of samples to determine what should get through, so you need to hear something for up to tenths of a second to decide to let it be audible.
> My 'ideal' soundsucker (sonic black hole) is a ceiling mounted device that projects a cone of silence. One possible way in which it could work is by using a phased array of speakers to 'fake' a larger one. But that ideal will likely never be reached due to limitations in physics, imagine the problem as applied to a wavy surface of water: create a wave pattern that cancels out the wavy surface in one circular area without touching the water directly.
You'd probably want a full network of microphones around your room for this to work, as standing waves will be set up at audio frequencies. It's nontrivial to handle reflections with data from a single spot.
You could do this if you could handle the reflections, but you would need sensors spread around the room (to detect sound before it was already in the cone) and it would only work at a single head height. You'd do it by intercepting the sound, sending opposite waves from above that reached the sound as it propagates across the silenced volume. If you're more than 10s of cm away from the band of silence, the desynchronization will start letting sound through.
It would also be less effective at higher frequencies unless you had head tracking, because the wavelength of sound is not far off from the size of your head.
Wireless is hard for this kind of stuff due to latency, wires are ugly but practical and for a first run I would definitely prefer a wired solution over none at all assuming it is even possible. An alternative configuration would be a cylindrical shape that is 'noise free', with speakers radiating outward, microphones would be set in a secondary circle around the first one.
I imagine this sort of setup would use a very large amount of computing power to make it work.
That only works in the free field. In a small room (defined as dimensions being larger than ~1/6th to 100% of a wavelength) you no longer have waves, the entire room is pressurized. And as you mentioned, modal behavior is also an issue.
If you're trying to measure the parallax of outdoor (free field) waves, that works in a truly free field, but once you have reflections (from, say, the ground) you have to account for that as well.
This exists today, it's just not a device, it's building materials. The more sound deadening you want, the more expensive the room will be. It's possible to deaden sound in this manner to the extent that many people feel uncomfortable[1].
___
I'm assuming one of the biggest things limiting sound cancelling is processing speed? being able to react to changing waveforms as they arrive at the ears
I use both (Bose QC35ii and 3M Peltor X5A) and I find the Bose is better in two ways: ear comfort and it doesn't trigger my tinnitus. It seems the Bose lets in just enough ambient sound that my brain doesn't go into a tinnitus-crescendo-loop.
Also, of course, the construction headphones don't play bluetooth audio.
Fitting both microphones and speakers in the device is the current challenge. The Bose device shows we are very close to solving that too, and the rapid shirking of wireless in-ear headphones is helping.
I put my sunglasses under my monitor with the lenses facing me and whatever is behind me. A rounded mirror works well too.
The silence is pretty addictive.
Why not just put a mirror on your desk?
I have NE headphones but they are too big for me to comfortable sleep with them (I tend to turn in my sleep)
Also from the paper: typical noise cancellation systems create local dead zones of radius ~1/10th the wavelength of blocked sound. E.g., you can block a 1KHz wave within 3.4cm of an error correcting microphone. Good enough for noise canceling headphones but not a whole room.
This work builds on an earlier finding that you can treat the window itself as a point source. Noise cancellation at its source is much more effective, so this way they’re able to create a dead zone the size of your apartment.
I didn't notice many sound isolating walls there either. Guess people who were born there get used to it.
One neat idea is electrostatic speakers! They're one of the more exotic speaker types, but have unparalleled quality at low volumes. However they are prone to distortion as volume increases and require high (100+) voltage supplies. They can be dangerous and fragile.
The idea is you stretch a mylar film very tightly into a rectangle, and then sandwich it between two metal meshes, with an air gap. By putting voltage on the meshes, static electricity pulls the mylar forward and back while keeping it almost perfectly flat.
You can put meshes (or ITO films) inside a double pane window to create a very even force over the whole window, making it an excellent transducer. It requires far higher voltages to move glass, though. Putting mylar in between the panes doesnt work (you need some free space to create proper cancellation- oversimplifying) and putting mylar on the outside is dangerous. Tricky problem.
In other words, they are saying that it is possible to keep your windows open if you want to and still not let noise in--not that you are permitted to cancel the noise, but must keep your windows open anyway.
I had initially thought this would be something about indoor CO2 buildup or something, but no.
People may forget themselves and lose sense of perspective. I have a bipolar condition where sometimes I'll pace my apartment and yell about anything and everything, if I lived in one of these places I imagine it'd exacerbate things and bother the neighbors too.
I haven’t spent a lot of time in Singapore but the time I spent there had visibility of about 50m from the burning of scrub/jungle in Malaysia and the air quality was abysmal.
https://www.researchgate.net/profile/Martin_Tenpierik/public...
This did get me interested though and am curious of what software libraries and solutions are out there for noise canceling. I would very much like to hook a mic and speakers up to a raspberry pi and get some of the road noise reduced. I'm not sure where to start with software though. I know the basic premise is invert the signal coming from the mic and output that. That's not exactly state-of-the-art though.
It sounds like this should work...
When it was on and NC was engaged, it was actually louder in the room when a car drove by. The counter noise was adding, not subtracting.
It's was a quick and dirty hack. I assumed the physics and algorithm they use requires the mic to be closer to the speakers and gave up. It would have been pointless to try to modify it further. That's why I was hoping there is a software solution that I could actually have a chance of modifying and e.g. fix the delay if that is the problem. Maybe even a ML solution.
https://www.youtube.com/watch?v=--c0tiIZG6o
This is by far the nerdiest channel I subscribe to and I LOVE it.
I live near a freeway and the cars don't bother me that much (I'm far away that they sound like white noise). But the motorbikes, however, are the works.
Some of them don't make that much noise, but the outliers make you go crazy. It's a shame really
The problem with creating nulls by cancellation is that you create peaks somewhere else. You could null out one person (maybe only one ear) somewhere in the room, but multiple targets will be really hard.
Or buy a box of standalone cancelers and stick them where you need them. Like the dog's collar.
Faster please.
I reckon you could probably do some extremely local noise cancelling (which would only work for a few people at most), but then the speakers don't only need to balance out the external noise, but also each other, which could require extreme volumes if the distributions of speakers is a bad fit.
Note that this is ~50% reduction in volume, roughly the difference between a loud and normal conversation. Noise cancelling headphones are more like 75%-87%, the difference between a loud conversation and a whisper.
Yes, it is extremely hard. The question is though, can it be done? Phased arrays are insanely hard as well, they do work though.
In the 80's there was a free space noise cancelling demonstration on a cross roads in a major city somewhere, I can't seem to dig up any references to it. IIRC that was a completely analog setup, I have no idea how it worked but they had a volume within which background noise was substantially reduced. I can't stand it when I am 100% sure that I read something but I can't find it.
A back of the envelope thought. A quad-pane window with the double-pane at outside to cut down the noise, a middle air gap, and then a double-pane inside. There's an opening at one end of the outside double-pane to allow air to go between the middle air gap and an opening at the other end of the double-pane inside to allow air to flow through. The ANC can be placed along the middle air gap to reduce the noise more.
.jpg){kind=link}
air in
=== ===================
| noise -> <- ANC |
=================== ===
air out
There are other issues regarding the impedance mismatch between the outside and middle air gap openings.
As you said, it's a very hard problem.
First, what you be the problem of creating a three dimension speaker array? Sounds totally feasible...
Second, is that really "the best" that we can do? I've read about a mesh of special design that you can put on your window that still lets you see outside and lets air go through, but cancels certain movement/frequencies, cutting off noise.
Honestly, people should just drill an extra hole in their walls, add a quiet fan and put a series of passive sound plates and other known geometry to cancel the sound. Or pipe fresh air from the roof.
mic -> fft -> secret suace analysis and filtering -> unfft -> speaker
A simple filtering would be a high pass filter, to avoid random high frequency sounds from constructively interfering producing more high frequency static.
Just a random tidbit, if you listen to rtings' examples or have a pair yourself I'd suggest playing some different colours of noise to see for yourself!
For what it's worth, since humans perceive sound logarithmically, a doubling sound of intensity feels like a constant (+3dB) increase of noisiness. This window would not even double sound intensity unless you're right next to it.
Edit: more importantly these are destructive waves, so if anything you’d actually reduce reflections back out into the world.
So for the person inside the apartment it sounds like a wall in the way, attenuating sound from outside, but for the neighbour across the street, it sounds like a hole absorbing the sound instead of reflecting it like a wall.
With enough points in a directional array it starts to resemble an acoustic hologram, with some remarkable one-way properties.
If you wanted to go really far with this, you could cover the exterior walls of buildings with dense arrays, and it would dampen street sounds for everyone in the neighbourhood, indoors and outdoors. In the street it would sound a bit like there were no buildings either side to reflect sounds back into the street, yet at the same time the buildings would still block sound from neighbouring streets.
Perhaps in future cities will do this.
It also works well enough to see it doesn't really do what you are describing. The energy from negative copy sound waves is being used to cancel out the original sound waves, the better it's working the less energy there is going to sound waves "escaping" to be heard anywhere else.
I'll do a 360 picture of it after it's done. like I did with the victorribeiro.com/3Dsphere but with picture instead of a render
Towels, acoustic panels and other materials are good at reducing echos but it doesn't really do much at all for reducing the amount of sound that can enter or escape a room.
If you had an open room with a hardwood floor, you'd likely get a lot of echos when talking normally. That's where things like acoustic panels help out.
If you want to dampen the noise of your neighbor's kids screaming like maniacs you'd have to do a pretty serious amount of sound proofing with other strategies. It's a lot more complicated.
I want to stop noise from coming in to my entire room, both acoustic and structural.
I'm extremely skeptical this is something that can be addressed by noise cancellation, either.
Just saying that there are probably lots of different noise reduction techniques that all add up their percentages, but these will only be put in place if noise pollution is taken as serious as it needs to be.
In this case, it will put pressure to avoid, or reduce, noise when possible (as it directly lowers costs). It's not only cars - all neighbors with a passion for loud music (or quarrels), repair works taking longer and louder than necessary.
Where the engine noise was noticeable was low speed intersections when cars would accelerate and the tire noise would be negligible.
Buses/trains are relatively quiet, outside of a few edge cases like tracks scraping or honking when someone's in their way - rare occurrences.
Also a fair amount of noise generated by cars is not the engine; for example, you have the sound of the tires rolling on the pavement.
I find it obnoxious and I am a motorcyclist.
While we wait for that why can't architects/planners take soundproofing more seriously (if they've considered it at all) and actually make the walls and windows inside a building soundproof. It's not even outside noise, I lived in apartments where I could hear my adjacent neighbors.
When I come to an intersection I have to be especially conscientious because pedestrians are use to engine noise bouncing down the road ahead of the car. People have walked out in front of me unaware of my existence. I normally mouth, “Surprise, motha fucka” or “I’m Batman” when that happens.
On one hand, I think it's dumb because why am I explicitly making noise? So I turned it off. But then I scared the living hell out of two shopping ladies when I unintentionally crept up behind them, and now I always leave it on.
[0] https://www.theverge.com/2019/7/1/20676854/electric-cars-art...
Agreed, so very much. I live across the way from an old-age care home and, based on stereotypes, you'd figure that would be quiet living. Not so much. Their landscaping crew gets out with leaf blowers every day, they have a weekly generator run-up test that lasts for half an hour and pulses with a deep bass, and every few hours on every nice day they pump out the best hits from the 1940s and 1950s on their outdoor patio.
Almost all of these are louder than the city's rules permit but code enforcement has told me that because both buildings face each other over a privately-owned parcel (one of these "privately owned public spaces"), the noise transmission rules do not apply.
I found this out after I called the care home, twice, to ask if they could maybe turn down the music or do the generator test later in the day (when more people are out and it would be drowned out by other ambient noise) only to be told, politely, to bugger off.
I like living in a city and am not going to move--it's not that annoying, compared to benefits I get in return--but sometimes I wish the commons weren't so tragedy.
But the thing is they don't have to be. Sure, you have to expect people talking, cars going through, people mowing the grass, the occasional honking. But even in the middle of Manhattan, the only noise that will wake you up in the morning are people being assholes or breaking rules. Special construction permits that have no business being issued (eg: jackhammers in the middle of the night), people screaming (why?), harleys motorcycles (why is that legal?), neighbors blasting music (you can hear it just fine, can you lower it a bit?), musicians in apartments (can't you use an electronic drum to practice?).
Everything's avoidable. People are just inconsiderate, and/or the problem isn't taken seriously. But no, it's not inherent to living in a dense area, unless you're talking about "being surrounded by assholes" being inherent to cities. Then yeah.
suburbs aren't really a solution because people can be assholes everywhere. But even if they weren't, current pushes to get rid of restrictive zoning means you won't be safe in a suburb for much longer anyway. We need solutions for noise in densely populated areas because we're not going to be able to avoid it long terms. The solutions all exist, they just need to be implemented and enforced.
My kids, brought up with it, were surprised to even be told there is motorway noise, they simply don't notice it.
I'm maybe 500 feet from a 2-lane road and about a mile from an Interstate in a fairly spread out area. It's not exactly noisy but with windows open and no music or anything playing, you definitely hear the road traffic.
And they do it deliberately. The concept of "loud pipes save lives" is so annoying. Maybe on the highway, but the way they rev their engines in neighborhoods is not necessary or even in town.
The even bigger concern is mostly that a moderately loud speaker system (>50-150 watts) can electrocute you. I mean that literally, as the portmanteau of electricity and execution. 1 kV is easily enough to put electricity through your heart; 50 milliamps would be lethal. 50 mA at 1 kV is only 50 watts, less than a laptop charger. A big set of electrostatic speakers can just stop your heart if you're very unlucky.
Finally I realized that I need NC for removing some fan noise like HVAC and server but I don't need superior one. I got Beoplay H9i for $300 and satisfied for both. Fewer battery life is cons.
Not sure I get it here either, since most cities I can think of have multiple highways going through them, but thanks for the clarification. Always glad to expand my understanding of language.
I really missed them on April Fool's Day this year. Like what's the point of even honoring the day if I don't get to start it by looking for the fake products in the TG catalog? Maybe I should just go back to bed.
[1] https://www.ebay.com/itm/10cm-Diameter-Focal-Convex-Mirror-L...
[7] https://www.amazon.com/Computer-Rear-View-Personal-Security-...
Sound isolation keeps sound from getting into and out of the room. It's a separate problem, and you can only solve it with mass and physical separation - e.g. building a room inside a room with massive walls and rubber isolation for the floor.
If you do it properly you have to pay a consultant to design a solution for you, because it's so easy to get it wrong.
Acoustic cancellation is used at the room scale to remove vibrations from sensitive scientific experiments. Its not the tech that only works on certain sounds, its the implementations.
Wireless only has latency if you let it! Plenty of bandwidth outside wifi and bluetooth stacks, and communication over infrared is always an option. You are correct that wifi and bluetooth have way too much latency, though- 50 ms is 15 meters of distance at the speed of sound.
Computing power is surprisingly relaxed. The problem of figuring out what waveforms to output from a line of speakers to create a given distribution of sounds is actually just a fourier transform, funnily enough. Creating a volume of sounds is just a 3d fourier transform. Both are unreasonably fast to compute, given how powerful they are.
If you want to know more about how the math works and what it applies to, check out fourier optics. IMO its one of the coolest natural phenomena.
Mentioned here: https://news.ycombinator.com/item?id=22078517
Airpods fare a little better, but I'd like something even more improved... if it could somehow let fresh air in and cool my ears a little too, that would be great...
I guess it's somewhat a matter of what you're used to. I grew up pre-Walkman and have just never gotten into the habit of wearing earphones like that.
I did forget to think that two ears would be like having two different people - there would be two target points where the sound would have to add up/subtract to the target.
20 dB is a ~4x increase in perceived sound volume, but a 10x increase in the actual pressure of the sound wave. So, oversimplifying, if you block off 90% of the sound waves entering a volume, the remaining pressure spreads out to 10x weaker waves... which are still 25% as loud. Keep in mind that this is covering 90% of the floor, walls, ceiling, doors and windows in perfectly sound-blocking material, which does not exist.
To reduce volume levels by 90%, you need to perfectly isolate 97% of the sound leaking in. You literally need to build a new room inside the old one. That's before you even account for the fact that your ears will adjust and sounds need to be much quieter to keep from picking up on them.
Preventing sound from exiting a volume is even worse. Sound has quite low absorption coefficients even in things like open cell foam; anechoic chambers rely heavily on shapes that trap sound and cause it to echo through foam dozens of times so that it's sufficiently attenuated before it bounces back out. Most reasonably airtight rooms are painfully loud because sounds you normally consider quiet (eg footsteps) are not attenuated as normal.
Keep in mind that even if you think a room is reasonably airtight -eg when you have an open window, your door closes far more easily than when the window is closed- it's really not at all. You've probably got vents etc that allow lots of air to move in and out of the room.
In a well-sealed room, sound will echo ~100 times (a second or two) before attenuation makes it much quieter. That pressure is just bottled up and it will escape through even tiny cracks, and if you were to listen at one of those cracks you'd hear much more clearly than if the room wasn't soundproofed at all. In that case, the soundproofing is just acting like a funnel or a crack in a pressure vessel. Unless you've got comprehensive soundproofing and a way to increase attenuation, all you're doing is causing the sound to escape from smaller spots.
When you see people recording and they have just a few acoustic panels up, the point is not to make the room any quieter. In fact they usually want the opposite- you want sound to exit the room as easily as possible, to prevent echoes. If you hang up too many panels, you prevent that from happening and you don't really decrease the volume of sound from the outside.
Acoustic panels are best used sparingly to dissipate or break up echoes from a very specific place, like directly in front of the recording, or behind electronics/noise sources.
For one person, a baffle of 10x 1cm sheets of plywood with a 2cm air clearance will do wonders (works out to be approx a 30cm cube with a 30x2cm slot at the front and back).
You can push ample air for one into a studio without any audible sound getting through.
Further, that figure isn't very helpful for fluid acoustics. Within the equivalent distance you instead would get tons of nonlinear effects, because fluid flow dominates acoustic transmission. In addition to heavily changing transducer loading, things like vorticity also start to dominate. The net effect is that near field issues arise much earlier, at more like a third of a wavelength. Still, only the very lowest audible waves and quite small rooms create non-acoustic behavior.
> once you have reflections (from, say, the ground) you have to account for that as well.
Ish. Only for quite high frequency sounds which change very quickly. Otherwise reflections tend to mostly just overlap with the primary source. For low frequency waves the distance between the microphone and your ears is much smaller than the wavelength, so you don't need to worry about multiple waves very much.
I have young kids at home. Those are the exact sounds I’d want to cancel!
Now, Sony has banking, internet provider, insurance, camera sensor, NFC payment companies as well.
Would we also boycott all of these, as well as smartphones that feature a Sony sensor for instance, if the goal is to be consistent ?
I’d totally boycott Sony BMG for life, but I feel it would be the wrong signal to boycott other independent activities, in particular as the headphone devision is one of the last bastion of trying to provide the clearest sound at a fair price, in a world where Beats and Bose are runaway hits.
I’m not boycotting Sony, I just associate their name with crappy products.
The mirrorless cameras aren't just pretty good, they're the new standard unless you have Canon/Nikon brand loyalty. I can't find the stat right away but IIRC Sony supplies more camera sensors than anyone else for smartphones (or maybe its just the high end ones)
I mean I'm not trying to change your mind, just adding my 2 cents that every piece of Sony hardware I've had was extremely well built and lasted years or decades. I have an old Minidisc player too I dig up every few years to listen to recordings I made back in high school.
Also, considering how much these thngs cost, too much money gets thrown out when just the inbuilt lithium batteries wear out eventually. I now avoid buying anything with embedded and unremovable batteries if possible.
https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Ex...
> We could have big houses, with windows that shutter in the summer mornings to keep out every bit of the too-early light of dawn, or shutter in the night to leave the stars absolutely untouched. We could have roofs that let in the sun.
oh god, yes please!
https://en.wikipedia.org/wiki/Roadway_noise
"...rolling tires driving on pavement is found to be the biggest contributor of highway noise which increases with higher vehicle speeds."
Most states have very lax inspection requirements.
Even in my state, which supposedly is one of the strictest on inspections, it's surprisingly easy to have a dangerous failing car pass.
Living near a busy intersection you hear all sorts of weird mechanical failures as cars brake and accelerate from the stoplight.
I have a weird obsession with road noise and how it relates to road surface construction.
Please let me know when you have it all built I'm very curious to see what it will look like in real life. And don't forget to take 'before' and 'after' readings with a sound level meter!
They have blessed me with some blissful naps, however. Possibly their greatest superpower is making robot vacuums disappear.
My first apartment was outside a level crossing frequented by Amtrak and Union Pacific. The federally required horn blasts - 2 long, 1 short, 1 long - overwhelm anything you might be doing or thinking about, resonate in your chest cavity. The building shakes, and the air becomes thick with diesel fumes and sediment kicked up from the railroad bed.
After an hour, I forget that the freeway is even there.
In Britain, within towns there's usually gates on either side of the road, so it's not necessary for the train to use its horn.
I too enjoy cycling and understand that there are serious safety problems involved with cars and bikes sharing the road and that and most of our cities have done a poor job of dealing with them. I don't think keeping around legacy noise pollution is the answer. It reminds me of this: https://xkcd.com/1172/
We have to stop treating noise as a mere annoyance or as something that "Karens" bitch about because of their priviledge.
It's polution, a health issue, something that ruins quality of life, and for people with certain health issues can be a chronic problem. It prevents people from sleeping, focusing, lowers productivity, make people "dumber", you name it.
In a lot of ways, the impact of noise can be similar to that of lead pipes. And we act like we can just tell people to deal with it, and that white noise machines and earplugs (hello ear infections!) are a solution (spoiler. I use both and it barely makes a dent in the noise sometimes).
Like? (Don't limit yourself to the easy-to-introduce-today; not everywhere has established road infrastructure, and your ideas could be used there.)
Increasingly, modern car drivers are enclosed in noise dampened, environmentally controlled environments with some sort of sound entertainment playing (music, podcast, talkback radio). So car drivers are less able to make good use of sound and other cues for detecting other traffic.
The lack of sound from hybrid cars, for example the Toyota Prius when accelerating in electric mode, has caught me by surprise while cycling. Not knowing you are about to be overtaken can be dangerous because there is an instinctive fight/flight response which can cause a sudden flinch or overreaction away from the surprise and you naturally turn your head to look at the perceived danger. As you are normally cycling on the edge of the roadway there is a higher potential to now accidentally ride over/into an obstruction (drainage grate, kerb, pothole) and come off your bike.
Intersection sounds like <35 mph, so you are agreeing with me.
In short, the road noise from tyres is due to air being compressed by the tread and then released again. It's basically a constant rolling version of clapping your hands.
Modern formulations of tarmac are designed to settle with air channels (called voidage) to provide an exhaust for that air, significantly reducing the volume. If you want more information on a couple of types, look up stone-matrix asphalt or open-graded friction course. Concrete on the other hand is notoriously poor for sound reduction, because the surface is so much smoother.
As a rough rule of thumb, quietened surfaces come in at 6-9db lower than a comparable non-quietened surface.
ARFC is another kind, made of recycled rubber mixed as a secondary aggregate. It's commonly used as a quiet and long lasting surface in parts of the US, and has the advantage of being a good product for using up waste tyres. In the UK we have different compounds, which do similar things. The M4 between Swindon and Bristol is a particular treat to drive on acoustically.
Undersurface is potentially an issue too. For example, concrete surfaced in mono-aggregate based tarmac has a tendency to resonate and "sing". Concrete with undulations does the same, though for different reasons.
I could go on for some time but it's kinda dull.
I find civil engineering is often quite interesting, because the tradeoffs and issues can be surprisingly inobvious.
I've always been fascinated by sound and how people perceive it. I'm also a classical pianist and guitarist, amongst other things, which may explain it, or be caused by it. Who knows?
It's not something I thought other people would care to read about though, hence never doing it. Maybe time to re-evaluate that.
