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Comment by foobarqux | Hacker News Reader

0.11 pound per square foot is what is being proposed. That's 108 decibels. Which is between standing next to a lawn mower and standing next to a car horn. I don't see how anyone will tolerate that in practice.

https://www.omnicalculator.com/physics/db

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It’s not accurate to convert .1 psf to dB because it’s an impulsive shape, not a continuous tone. And human loudness perception depends on how smooth (low frequency) the shape is

> It’s not accurate to convert .1 psf to dB because it’s an impulsive shape, not a continuous tone. And human loudness perception depends on how smooth (low frequency) the shape is

Sorry can you explain more? It's just the definition of dB (?)

And it's less impulsive than you imagine, go to youtube to listen to the sonic boom + continuous roar.

The FAA has no criteria about the "texture" of the sound and there is no reason to believe the allowed planes will differ substantially in this respect compared to every other supersonic aircraft in the past.

On a typical day, the atmospheric pressure varies by maybe 150 Pa, or 3 psf. By definition, that’s 137 dB. But it’s imperceptible because the rate of change is so low.

Obviously it is assumed we are talking about frequencies in the range of the audio spectrum (which a sonic boom is). Your point has nothing to do with the dB scale.

Yeah nah. For all relevant level metering you use a A-weighting curve (weighting the frequencies by human ear sensitivity) so that is not how any of that works.

A sonic boom doesn't exactly average out over the length of the day, though, does it?

Back in the 1960s (!) the military would fly supersonic over the town I lived in. I always enjoyed the boom. I would also open the window during a thunderstorm or go sit on the porch because I enjoyed the incredible electric display and the booms.

Military gets away with things that private industry doesn't. Supersonic passenger planes would be flying every day on a schedule, far far more than military. Commercial planes are also rated for far more flight hours.

Yes, the military ones were infrequent. I'm sure it would get annoying if it was too often.

> Military gets away with things that private industry doesn't.

For good reason. You cannot train for hedgehopping to avoid radar detection without flying low with firewalled throttles.

Overland private supersonic travel should not happen, it would just be a massive unpriced negative externality.

The lower the plane flies the fewer people end up hearing the boom. The denser air also requires an absurd amount of fuel to fly through. Commercially uneconomical. Even the military only uses low level supersonic for a last dash to the target.

When Boom was testing last year, the sonic boom never reached the ground, as I recall. That can be arranged at higher altitudes, but doesn't work at low ones.

That's only possible under specific climatic conditions where there's separate temperature/pressure layers. Which is why they asked to repeal the ban on supersonic flight over populated areas. If they actually thought it wouldn't make noise they wouldn't be asking for the rule to be changed.

The rule bans the supersonic flight regardless of whether it's audible or not, so they'd still be asking for the rule to be changed.

They didn't ask for only a non audible change, because they know that it will not be. It's just marketing and misdirection because the truth is much less rosy.

Memories of a kid on a road trip...Interceptors taking off low, at full afterburners, in the dark of the night, screaming across the highway, for their practice sorties...

I am more anti-(manufactured)-war than most, but these sights were the stuff of goosebumps (the good kind).

The sound of freedom!

Dunno about that, but sure is a heck of an engineering feat and an audiovisual spectacle.

Back in the 80's the British air force would fly ridiculously low over the rural village I grew up in, certainly lower than they were meant to be allowed to - everyone hated it. You'd be minding your own business and then just about shit yourself out of nowhere!

I find it so bizarre that anyone would be upset about this instead of thankful for the protection.

Yeah, I often have military flight training over my town, and I don't find the sonic booms particularly bad. I barely notice the planes unless they fly close to the ground over my house.

I'm not sure how the sonic booms of fighter jets compare to passenger planes, though.

I can't stand military jets over my neighborhood. I get irrationally angry every time I'm walking somewhere with my wife and we both have to completely stop talking for two blocks because some F-14 is blasting around over our heads. They are just unbelievably loud.

The last American F14 was retired 20 years ago.

My only experience with a sonic boom was in D.C. a few years ago when fighters were scrambled to intercept a learjet which had depressurized and everyone onboard was unconscious. I believe it ultimately crashed somewhere in VA or WV. Anyway, my windows were open and the "blast" was startlingly loud, but not like a detonation. More of a gentler push like a large fireworks explosion. It was both a loud sound and a pressure wave sufficient to move the curtains in the windows. There were emergency services responding all over the city looking for the source of an explosion.

I guess we'll get used to it if that kind of things becomes routine? I'm not sure.

My guessing from the couch would be they were further away than you might have thought. I was up in the mountains when a couple of fighters flew close with a boom, and it was one of the loudest things I have experienced.

Yeah that's entirely possible, I have no idea what their actual flight path was.

You could have checked adsb exchange.

It seems like that is the limit. the proposal:

https://www.faa.gov/newsroom/ARM-260115-001_Supersonic_NPRM_...

... also alludes to new designs where the boom doesn't reach the ground. It also talks about primary and secondary booms.

Will folks with these planes eliminate risk of going > .11 psf by having the boom stay off the surface?

Because it's not continuous sound in one spot like a leaf blower is.

There is a substantial noise beyond the initial boom which is very loud even relative to the main boom. But even just a half second of a car horn going off right next to you every so often is intolerable.

People finding a way to tolerate what was previously considered intolerable is pretty much the story of civilization.

I'd argue that civilization is the story of people finding ways to overcome what they previously had to tolerate.

If supersonic flight is so expensive that less than 1% of the population can enjoy it its not clear why the rest of us ought to tolerate it

You have to start somewhere before you can build towards an economy of scale that makes it affordable. If people used your same logic about regular airplanes, we wouldn't be using them today.

Supersonic flight will never be suitable for the masses compared to normal flight due to basic physics. It will always require much more expensive planes and more fuel.

It's not more viable now wealth inequality just means that there are more rich people to benefit.

>Supersonic flight will never be suitable for the masses compared to normal flight due to basic physics. It will always require much more expensive planes and more fuel.

You could have used the exact same argument for normal flight 100 years ago. Supersonic flight being more expensive than normal flight doesn't mean it will always be too expensive for the masses unless you assume there'll be no more economic growth ever.

Physics doesnt change. It will always cost more energy to fly faster.

Relatively, absolutely, but look at computers. Yes, more computing still costs more than less computing. Physics hasn't changed, but the cost of computers has. I have, in my hand, for part of a couple months of middle class wages, more computing power than existed in the world in 1960.

Yes and now wafer costs are going up for n+1 node, because of physics reasons.

There are 28 000 passenger flights in the US every day, imagine the noise under major corridors if a large percentage of them was supersonic.

What are we talking about? 5% more? 200% more?

I'm still waiting for Tesla's plan to come true where the rich paid for development before scaling up brings the prices down. The luxury economy of scale is about as realistic trickle down economy

> still waiting for Tesla's plan to come true where the rich paid for development before scaling up brings the prices down

The low-volume, high-priced rich-person toys (Roadster) finance the scaling up that enables lower-priced mass-manufactured product (Model 3).

Get those rich people out of the private jets and into the supersonic ones. Then the rich people currently in first class can move into the private jets.

Eventually, that means that there will be some seats in the back of the regular plans for everyday wage slaves.

Its not clear why you would think any of this works this way. Not one thing you said makes sense it's like a weird trickle down economics for flights as if better steaks would get oliver twist more gruel

Food is different from airplanes. On a middle class salary, I could afford to take a flight from Atlanta to Liberia and back for $300. Or $250 to get to Vegas and back. Spirit recently went out of business, but in 100 years I bet supersonic jet travel will be available to the middle class.

Liberia the African country or Liberia the city in Costa Rica?

It's worth noting that the initial supersonic bans came as a result of sustained sonic boom testing over the same population: https://en.wikipedia.org/wiki/Oklahoma_City_sonic_boom_tests

I disagree. The more that I travel, the more that I notice the trend: The richer you become, the quieter you become. Even in the same country, income level seems to strongly correlate with how loud you are in public (and private).

> But even just a half second of a car horn going off right next to you every so often is intolerable.

You must not have a neighbor with a car whose alarm constantly goes off at random points throughout the day right outside your window. You eventually don't notice it. Speaking from experience

live by a railroad track. takes about 6 months till you don't notice it. at all.

Depends on the frequency and duration. Lived near some tracks for years and what got me was waking up in the middle of the night for that freight train that was irregular. The regular passenger train I got used to though.

To state the obvious, it's better if it's calm:

https://www.eea.europa.eu/en/analysis/indicators/health-impa...

On getting used to it, people adapt in that they stop consciously noticing the noise, but it's still constantly processed and grinding on one's environmental awareness.

I actually do, and I still notice it every time. Some asshole across the street rides a motorcycle and every day he revs his motorcycle which sets off the alarm of some other asshole's van.

> That's 108 decibels. > I don't see how anyone will tolerate that in practice.

Oh! Really?

https://earinc.com/gunfire-noise-level-reference-chart/

...yes, really? Gun fire is indeed stupendously, dangerously loud, which is why we have suppressors and heavy hearing protection for them. And there are indeed significant public/legal fights around outdoor gun ranges that end up near habitation (even if it's not the range's fault at all but rather because construction moved towards it).

So I'm not really seeing how that's an argument that people not wearing earpro would be fine with regular 108 dB booms over where they live/work. People aren't happy even about small engine noise and rightfully so, and it's one of a few core reasons for switching to electric.

Most gunshots people hear are not right next to them and so won't be anywhere near 108 dB to them.

also, there are neighborhoods with extended amounts of gun violence and discharges and I can't say that the residents "don't mind it"

In this case they mind getting shot at by stray fire, the noise is a secondary concern.

Keeps rent down tho.

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