As others have stated here, you can hear the sonic boom of planes flying by at a fairly high altitude, ~80 000 ft. At what altitude would the sonic boom no longer be noticable at sea level? To add to that, is there any relatively "simple" method of estimating sound dissipation with altitude?
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“Noticeable at sea level” will be a function of multiple parameters in addition to altitude (e.g., Mach, flight profile, weight/lift, aircraft shape, day-of atmospheric properties, ambient noise at ground level, inside/outside, etc.). That said, relative trends of boom strength with altitude can be found multiple places in the NASA’s so-called boom bible, or SP-2014-622. For example, see page 135 and figure 5.3. 
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As an observer, you hear the Sound Pressure Level (SPL), which comes from a source emitting sound at a given Sound Power Level (SWL).
According to this source, the SWL of a supersonic plane may exceed 200 dB. In the same source, a formula for computing SPL a given distance is also shown.
You can find an online calculator for that here.
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7$\begingroup$ Please include the formula inline. The source link is a good citation, and appropriate for extensive supporting information, but the core piece of information should be directly included in your answer and not require following the link offsite. $\endgroup$ Commented Feb 7, 2022 at 20:56
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$\begingroup$ Interesting beginning of an answer, but voting down for the reasons @MaxPower cited. There is no actual answer here, just a roadmap toward potentially calculating one. $\endgroup$ Commented Jul 21 at 18:24
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Dissipation of sound waves over distance depends almost entirely on variety in both composition and density of the material it travels through. This is why vertical propagation of sound is way more restricted than horizontal. So much so in fact, that a sonic boom generated by an aircraft at high altitude clearly heard at sea level at one location, may be completely unnoticeable as the same aircraft passes over a location a hundred miles further down its flight path. The altitude is more or less insignificant, unless it is clearly way too close or clearly way too far away. It's the stuff in between that matters.
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The International Space Station orbits the Earth at Mach 25, at an average altitude of about 250 miles (400km) above sea level, and we don't hear any sonic booms from it. In space, the air density is so low that there aren't enough particles to bump into each other to create a boom.
The ISS's avg altitude is 250 miles, but it can get as low as 174 miles, and we don't hear any booms even then. I assume then that the altitude where the boom goes away is somewhere between 60,000 ft (where the Concorde flew and did for sure emit a boom) and 918,000 ft (174 miles, the lowest altitude of the ISS, which for sure doesn't emit a boom).
Actually, gonna add this as well: "space" technically begins at 50 miles or 264,000 ft (well, unless you're not American -- then it begins at 62 miles -- but I digress, the difference is so small it doesn't really matter for what we're discussing). Because there are already so few (if any) air particles up at those altitudes, I think it's safe to say that a boom is extremely unlikely or impossible even at 50 miles (or maybe even a little under 50 miles) above sea level.
Best bet would be to not use a plane, though. Planes need to take off on a runway, gradually climb, gradually descend, and land again on a runway. Even though it won't emit a boom in cruise, it will for sure emit them in ascent/descent, which will be pretty long distances, since you need a long distance to climb to / descend from your cruise altitude. Those distances will be not-insignificant percentages of your total flightpath.
So instead, launch straight upward like a rocket, then transition to level flight once you're close to your cruising altitude (take 50 mi as the transition altitude, and 62 mi as the cruise altitude, just for example), cruise, then transition back to vertical descent near your destination, and land vertically like a rocket. The sonic booms, which will only be emitted in ascent/descent, will be emitted in one small isolated ring surrounding your launchpad & one surrounding your landing pad. Which won't be a problem if the areas immediately surrounding your spaceports are pretty empty. Easy to have, since most big airports today are surrounded by empty space anyway (bc they are located outside their served cities). Or just put your spaceport in a lake/offshore.
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$\begingroup$ Welcome to Aviation SE, T_S. Can you edit your answer to stick to aviation, not spacecraft? That would be on topic at other SE sites, not this one. $\endgroup$ Commented Jul 16 at 22:26
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$\begingroup$ @CamilleGoudeseune but was there anything inherently incorrect about the answer? Just curious, please let me know if there is $\endgroup$– T_SCommented Jul 25 at 22:40
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$\begingroup$ Nothing incorrect. Clever to contain the boom by flying vertically while in atmosphere. But still off topic, so move most of these ideas to a spacecraft SE site. $\endgroup$ Commented Jul 27 at 18:04
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$\begingroup$ @CamilleGoudeseune My answer wasn't off topic. I gave the relevant answer to OP's question. If anything, by your logic, OP's question would be off-topic for the Aviation site, and he should have asked it on the Space site. It isn't off-topic to give the most relevant answer to the question presented. $\endgroup$– T_SCommented Aug 10 at 15:49
We don't hear meteors at all... I beg to differ. In 2013, windows were smashed, buildings were damaged and people were injured as a result of the shockwave of a meteor near Chelyabinsk, Russia. Smaller meteors may be heard too, but the smaller the meteor, the more faint the noise it makes. Note that due to distance the sound has to travel, there is a long delay between the sighting of the meteor and the arrival of the sound. $\endgroup$