I used it about 10 years ago to take raw audio of paintball guns shooting and help pre-process said audio for analysis of shots per second.
It was great for a bunch of reasons:
- it could so a frequency analysis to show me which frequencies were present in the audio
- I figured out there was the frequency of the sound when the ball left the barrel but also a frequency for the gun's firing mechanism
- I could then do a bandpass on just the frequency of the ball leaving the barrel
- It then let me convert the audio to a numerical format that made analyzing the peaks and valleys much easier in Perl
- The end result was I could accurately calculate shots per second given just a raw recording and some processing time
Same for any topic in HN that people manage to have very intense and niche knowledge for. Maybe I have the same odd knowledge about some other thing, but I don’t find fancy lock washers as brain teasing as figuring out a helicopter route from a YouTube video’a left audio channel.
The audio signal is split left and right with the announcer on one and the telemetry on the other, it's easy to have some telemetry bleed over into the voice channel.
The antenna on the helicopter is programmed to always point at any one receive antenna and the receive antenna uses that data to track the helicopter to maintain line-of-sight for the video feed.
I believe many use cases of this have migrated to fully digital signal chains so the days of the weird audio may be ending.
https://news.ycombinator.com/item?id=7160242 (82 comments)
I thought it seemed familiar, though the details were evicted from my LRU brain long ago. Cheers.
A kind of funny thought — maybe something that was supposed to be grounded ended up floating, because the reporter was, uh, not in contact with the ground.
Anyone know what that is?