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Comment by xrd | Hacker News Reader

Very interesting to see how the noise of jet engines declined significantly. While reading the article I kept thinking, it feels like investing in noise reduction would really pay off, and then a few paragraphs later, there it was.

I'm also intrigued by small airports, like the one in Rio, Santos Dumont. The shortest runways in the world.

If you could reduce noise and control pollution, it is very nice to have an airport accessible by mass transit, like in Portland, Oregon. Feels like a sweet spot for government intervention.

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> Very interesting to see how the noise of jet engines declined significantly.

I know people who used to live under the flightpath of Concorde arrivals/departures.

Lets just say they were very happy when Concorde was retired from service. ;-)

Obligatory YouTube movie from 2007: https://youtu.be/i1ShTUVIzCI?t=41

Some small airports made sense at the time they were built, but no more (either because planes are bigger now or because construction around the airport was not adequately restricted in ensuing decades. Congonhas in Sao Paulo is an example of this, where it can only handle smaller domestic flights now because of the way the city has grown around it.

Here's a satellite photo: https://static.wixstatic.com/media/a27d24_a65c83caab794facb0...

(it would be like when you're landing at Reagan airport in DC and descending over the water... except that it's skyscrapers)

...and here's a story about Congonhas airport:

https://admiralcloudberg.medium.com/culture-of-chaos-the-cra...

which reminds me: maybe people don't oppose airports just because of the noise, maybe they're also worried about plane crashes (I know the chance is low, but probably much higher for those living near an airport than for the average passenger).

I have several Brazilian friends (mostly in/around Campinas) in SP state who refuse to fly in/out of Congonhas because of that risk. Thankfully now Viracopa is even more convenient and nicer.

Honestly, the irritating thing for Americans flying to Brazil is the frequent need to fly into either Rio or SP and then domestically transfer to the other, due to paucity of flight options [at reasonable prices].

Yet, airlines fight deary for slots at Congonhas, because lots of people want really badly to land there.

The same can be said for Santos Dumont, that requires specially adapted planes, with reduced capacity to fly there. Or Pampulha that is more extreme, and airlines keep entire models of planes on their fleet just so they can fly there.

I wonder if open (unducted) fans (if they catch on) like the CFM RISE will reverse this trend.

https://www.youtube.com/watch?v=ojVNOj-q3SQ

https://www.youtube.com/watch?v=XkHKet7rp4o

Going from 120-110 down to 100-90 isnt really a significant decline, it went from unbearably torturous to really annoying. Airports nowadays still create significant noise pollution in their surroundings.

Yes, from the graph it seems we've almost reached the asymptote and noise isn't going down much from here.

>it went from unbearably torturous to really annoying

That's like saying the difference between getting stabbed and pushed isn't big since both are physical assaults. It is. 120 is at the level of ear injury and pain even in the short duration of a takeoff. 90 isn't.

You are aware that DB is a logarithmic scale?

I'm not going to say 100db isn't loud but db is a logarithmic scale, so even 110 down to 100 isn't a 9% reduction but an order of magnitude drop. Literally the difference between a jackhammer and a nail gun.

Sound drops 4x for each 2x increase in distance from the source. So another way to put it is, if you cut sound by 10x, you are cutting the distance of severely noise polluted area around by more than 4x.

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