5 ms·
I wonder if there was a local loudness maximum on the globe diametrically opposed to the volcano. As the advancing wave makes it half-way around the globe, it
by recursive 6y ago
I wonder if there was a local loudness maximum on the globe diametrically opposed to the volcano. As the advancing wave makes it half-way around the globe, it seems like it would converge simultaneously on a single point on the opposite side.
- mynegation 6y agohttps://news.ycombinator.com/item?id=8386018 https://news.ycombinator.com/item?id=8386018
- pmiller2 6y agoI was interested to learn that the loudest possible sound on Earth would be 194 db. [0] Krakatoa apparently "only" clocked in at 180 db, meaning the loudest possible sound is about 5x louder than said eruption.
- gns24 6y agoThe article states that the sound from Krakatoa was well over the 194dB limit.
- OldHand2018 6y agoIf a reader were skimming the article, they might have missed that the 172 decibel "reading" was measured at a gasworks 100 miles from the eruption!
- greypowerOz 6y agoIIRC A 10 Db increase in SPL is perceived by most people as a doubling of "volume". thr article mentions this too... its hard to get a feel for log scales lol.
- pmiller2 6y agoYeah, it's funny how humans don't really comprehend logarithmic or exponential growth, yet, the whole reason we use a log scale for stuff like sound pressure is that our nervous system has a logarithmic response curve.
- singhkays 6y agoTIL how the decibel scale works. Genuine question, how's the difference between 194db and 180db only 5x? Shouldn't it be more than 10x?
- adamjb 6y agoThe decibel is defined as a tenth of the log10 of power, so power doubles every ~3dB. Amplitude and pressure are proportional to the root of power, so amplitude doubles every ~6db. Loudness is roughly proportional to the root of amplitude so it doubles every ~9dB. This leads to confusion when people don't specify which quantity they are comparing.
- s1artibartfast 6y ago194 db is the loudest possible sound, where sound is an oscillating pressure wave. Pressure above 194 db become Shock or blast waves, which are a pressure pulse. https://waitbutwhy.com/2016/03/sound.html https://waitbutwhy.com/2016/03/sound.html
- T-hawk 6y agoIt wouldn't be simultaneous. The difference in great-circle lengths based on nonspherical oblateness (tens of miles) would account for up to a minute difference in arrival times at the antipode. At most it would be a sustained rumbling. And on a global scale, there are many differences in pressure and wind speeds and temperature that do slightly alter the speed of sound. I don't know the magnitude of that, but it would further disperse the arrival times at the antipode to at least some extent.
- saghm 6y agoThere would still have to be some place that the sound waves met, right? Is there any way of figuring out where that would be?
- monktastic1 6y agoNo, there doesn't need to be such a place (even on a surface that's much less irregular than the Earth is).
- T-hawk 6y agoThey all cross the antipode, but not at the same time. There is no point where they all meet at the same time, if the planet is oblate rather than spherical, or has other irregularities in pressure or temperature or surface terrain.
- pwagland 6y agoGiven that it started at a "point", it would go outwards in a circle, so you would end up with a "line" where sound from each direction crossed over. In theory, you could end up with a point where they all met again, however due to the focusing effects of the various landscape, and ambient pressure differences, this would rather be a diffuse area than a concentrated point, just like the lines where the sound met wouldn't be straight either. This, combined with that the fact that on the on the "other" side of the world it was really only detectable by barometric readings means that you would be hard pressed to notice it, even along those lines and or point.
- DrBazza 6y agoFWIW the antipode of Krakatoa is near Medellin, Columbia.