The voice of Utah's arches – Ambient seismic vibration sped up 25x • Hacker News Board

Re: The voice of Utah's arches – Ambient seismic vibration sped up 25x

#41

Post by mateo1 » Tue, Mar 08, 2022, 11:16 AM UTC

Cerium wrote: post #12

I worked on a seismic monitoring system for civil engineering structures. We recorded data at 200 Hz (though all the interesting content is in the zero to 15 Hz range). Once I tried this experiment with some of the data from a bridge in a harbor. It was very cool, you could hear so much going on in the bridge. Ambient seismic vibration is something of a hidden world around use. With a very sensitive accelerometer you…

Also depending on the scale, seismic surveys are seriously affected by nearby roads and construction, where "nearby" can mean several km in some cases.

Re: The voice of Utah's arches – Ambient seismic vibration sped up 25x

#42

Post by frumiousirc » Tue, Mar 08, 2022, 2:14 PM UTC

jmiskovic wrote: post #39

Is there a name for shifting the recorded phenomena into the part of spectrum where humans can directly sense it? Or for converting signals into different medium, so that we can hear or see signals that we couldn't sense otherwise? I'd like to know the name so that I can hunt for more examples and applications. A good example is Dwingeloo radio telescope where they convert pulsar signals into audio in realtime so tha…

I think this is simply using one rate for sampling and another for playback.

Another comment suggests seismic samples like these are taken at 200 Hz. That is comfortably above the rock vibration frequencies of a few Hz. If one simply plays back these samples 100x faster the result would appear as 20 kHz sampling and the signal power that was originally around a few Hz would be heard at a few 100 Hz. The audio sounds a bit higher in frequency so perhaps these numbers are not precisely what were actually used but they give the idea.

That's just the shifting. Accelerometers are used for the original sampling so there must also be some sort of pre-processing in the original sampling domain (the example 200 Hz time base) to convert acceleration information into displacement. This is a 3D displacement so then some other transform must be applied to represent the 3D vibrations with a 1D model.

Re: The voice of Utah's arches – Ambient seismic vibration sped up 25x

#43

Post by carapace » Tue, Mar 08, 2022, 4:58 PM UTC

aahortwwy wrote: post #35

carapace wrote: post #32

I long time ago I had an audio cassette of recordings from, I think it was Voyager, of the ambient interplanetary EM signals it encountered transposed somehow into audio. It was eerie and wonderful, a little like whalesong, and one of the most haunting and beautiful things I've ever heard.

Symphonies of the Planets , perhaps? https://rateyourmusic.com/release/album/various-artists/symp...

Cheers! That sounds like it but it's hard to be sure after so long.

https://archive.org/details/VoyagerRecordings-SymphoniesOfTh...