manicdee33 t1_j98rzsh wrote
The USA is best known as the country that will do anything to avoid using the metric system.
Paper this article is based on: https://asa.scitation.org/doi/10.1121/10.0016878
> Significant results include: (a) the solid rocket boosters' ignition overpressure is particularly intense in the direction of the pad flame trench exit; (b) post-liftoff maximum overall levels range from 127 to 136 dB, greater than pre-launch predictions; and (c) the average maximum one-third-octave spectral peak occurred at 20 Hz, causing significant deviation between flat and A-weighted levels.
I'm just lost on how they quantify the "crackling quality" :D
unpluggedcord t1_j98ubi6 wrote
Fwiw the national measuring system is metric, it changed in the 70s. But nobody adopted it.
Primary_Skill3749 t1_j999970 wrote
I don’t think that’s completely accurate as many scientific industries like medicine use metric as a standard in the U.S. Even nasa was using metric well before the 1970s.
unpluggedcord t1_j999dgj wrote
I’m referring to the law that was passed by congress and signed by the president.
simpliflyed t1_j9cc3u4 wrote
I think they meant the bit where you said nobody adopted it. Pedantic either way!
[deleted] t1_j990q77 wrote
[removed]
billsil t1_j99epup wrote
Depends how much it pops.
136 dB is really loud. Also Bels are not really a unit. You take the logarithm of a pressure relative to 20 microPascals (the threshold of human hearing), so it's unitless. Deci-bels are 1/10 as large as a Bel and just make the numbers easier. Otherwise, we'd be talking about 13.6 Bels.
Beyond that I understand part of it. An octave is a power of 2, so 20 Hz to 40 Hz. The 1/3 octave part means that between 2 octaves, you have 3 bands. So for 20 Hz, the range of interest is 20/2^1/3 to 20*2^1/3 (or 15.9 to 25.2 Hz).
The USA is best known as the country that will do anything to avoid using the metric system.
That quote is metric and English friendly.
freds_got_slacks t1_j9bdpqg wrote
In this figure from that paper, while the flat peak is 120 dB centred around 20 Hz, with an A-weighting this only translates to about peak 95 dBA around 200 to 1000 Hz.
Measurements for occupational safety are done with A weighting, but would there be any safety concern with an unweighted 127 dB SPL at 20 Hz? or is A weighting still sufficient ?
Edit: higher res figure
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