9 ms·
> Heck, a decade and a half ago there were claims that governments could narrow a search for an audio file upload based on the deviation from 60hz on the power
by absorber 6y ago
> Heck, a decade and a half ago there were claims that governments could narrow a search for an audio file upload based on the deviation from 60hz on the power line noise - in an audio recording.
Wow. Any source for this?
- RisingFusion 6y agoI think it was referring to Electrical network frequency analysis, which is to find the time that the recording was made. It compares small changes in mains hum frequency to historic records of the changes. I am not sure how it is in the US, but the UK grid has a single frequency over the network so it wouldn't work for finding the location.
- teruakohatu 6y agoThe propagation of waves is very fast, but wouldn't distance from multiple large sources or sinks fluctuate the frequency just slightly based on distance?
- torified 6y agoDistance doesn't change frequency, only velocity. Doppler effect.
- wiml 6y agoHere's a brief piece on the practice: https://www.bbc.co.uk/news/science-environment-20629671 https://www.bbc.co.uk/news/science-environment-20629671
- grugagag 6y agoAnd how about if the recording device was running on batteries such as a unplugged laptop or a smartphone?