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Viral shortform video is often augmented with subtle glued-on sound effects, but here's an interesting one - the background noise was "looped" for around 9 extra seconds to drive home the wow effect :)
Update: One of the places that had this ultrasonic beep from their PA system has now stopped using it!
There's now a much quieter tone at a much higher frequency, outside anyone's hearing range for sure, which only shortly appears every now and then. Maybe they upgraded their sound system?
It's amazing how noise resistant LoRa is. It took me a while to realize that there can be plenty of perfectly decodable LoRa traffic even though the recording spectrograms look empty.
Here's a complete Meshtastic GPS position message (~50 chirp symbols each 250 kHz wide) buried in noise and some kind of smart meter traffic. I got a correct CRC after just 1 parity flip!
@windytan I also noticed the same pattern before. Still couldn't figure out the theoretical reason behind it, but I recognize the pattern kind of resembles an aliased sine wave
sin(x^2 + y^2)
x,y integers.
that I played a bit with before:
https://krasjet.com/eidos/cinoma/
The input audio in this case is a feedback loop constructed with two mic/spk pairs.
Whenever I run sine beeps through a home-made spectrum visualizer, and I use the square window or the Tukey window, I get these weird-looking vortices...
They stay the same size and shape regardless of FFT size, but they get bigger with bigger window overlap.
It might be a bug because I don't see it in other software. But it's pretty
Redsea v1.2 can now receive little pictures sent via RDS2 by some radio stations - usually these would be station logos meant for car radios. For now, this feature has very much an "engineer's UI" :)
Here's some logos our contributors have seen so far...
Daniel Estévez
kst