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
Then I used sox to extract loud but low frequencies, and since I could hear it correlated with road speed I was able to verify that it was a particular bearing in the front propshaft by working out the relationship of frequency and gear ratio.
All without crawling underneath and getting oily!
Makes me wonder how many lived experiences I take for granted that are totally different for others, and likewise the lenses through which others see the world that I would never imagine.
Completely aside, I think what you describe is going to soon be considered an arcane art - I fear "machine learning" is going to be the catch-all to describe what is really just pure math.
In the past for commercial audio analysis, I've used ArtemiS Suite from Head Acoustics for similar requirements. It would trivially do all of those things, including the Perl (well, what the Perl did).
I think it's really fascinating from a UI perspective, the multi-column separation of the project, audio files, analyses (chained back to other analyses where appropriate), graphics, and report generation makes it really flexible. Rather than pointing and clicking through a wizard each time you want to accomplish something, or up-arrowing in the command line to a previous entry, you set up a pipeline to accomplish that thing and then iterate the pipeline intake over all your inputs and it spews the outputs you need. And all that from an intuitive GUI with lots of graphical feedback, rather than a command line with more difficult discovery of features.
It changes your activity from executing commands one after another to engineering a script to execute those commands automatically, you almost can't help but make something reusable.
Tragically, it's locked behind a 4- or 5-figure license cost. Not a big deal when you're using it for testing automotive products, but not exactly accessible for paintball hobbyists.
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.
I've forgotten now which ep it was but I always fancied trying to pick them off the audio and decode them to see if there are any clues in it.
SSTV is another distinctive one, and the Aphex Twin track "Bonus High Frequency Sounds" is a pic of Richard James in his studio. Often wondered about the SSTV-like feedback in that Radiohead track, too...
That did not play particularly well in the UK, to put it mildly. Not sure if it was meant to be public relations for terrorist bombers...
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.
If two spaceships from different parts of the galaxy were ever able to meet, would they experience the biggest static electricity shock in history?
Apparently this is not an issue with terrestrial space stations, because spacecraft only accumulate something like an 80V potential as they travel through the atmosphere. But what about another star system that has sailed through who knows how many charged nebulae?
Anyone know what that is?
Ham radio operators use it for rovers and balloons, among other things. News choppers use it to report their position. If you have a radio, you can hear amateur APRS on 144.39 in the United States and 144.80 in Europe. There is even an APRS digipeater on the ISS at 145.825 MHz FM. You will hear a few APRS stations being repeated on most passes. The whole APRS network is actually pretty cool. If you have an SDR, decoding is pretty straight forward: https://www.w8wjb.com/wp/2021/03/21/decoding-aprs-packets-wi...
I believe the news helis use the same protocol but with obviously more frequent updates, but I've never tried to intercept it.