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  • Hacker News
  • AFAIK started by a fellow HN’er
    by dzhiurgis
  • Wouldn’t a purpose built Esp32 with microphones aimed at the sky do a better job? It would be always on, better directional targeting.
    by reboot81
  • I believe Ukrainians had already deployed such a system. This is specifically designed to use old Android phones already sitting in a drawer somewhere without any other use, and most importantly by anyone without technical skills.
    by rdtsc
  • For those interested there is an open source radar based phased array project here: https://github.com/NawfalMotii79/PLFM_RADAR

    I may have even discovered it from hacker news, I forget now.

    by kamranjon
  • I remember seeing this on HN when it was first submitted. I honestly think that project is either a scam, an elaborate hoax, a cover for a Chinese company selling radar systems or a three-letter-agency honeypot.

    The files [1], [2], [3] on Github (once featured on README and on some articles) depict what I presume is a Chinese built radar which you can see here [4], [5]. I also suspect this might be a honeypot since Instagram - of all places - is full of accounts offering these radars [6], [7]. Some of the contributors on that projects are heavily leaning into AI. Git project history is suspicious. Discussions on the issues seem very artificial. I remember having bunch of notes on this project, but can't find it now. Just looking at it from outside, nothing about it seems real.

    [1] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...

    [2] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...

    [3] https://github.com/NawfalMotii79/PLFM_RADAR/blob/main/docs/a...

    [4] https://www.cloudwalkerfpv.com/product/CW-t20.html

    [5] https://www.militarysignaljammer.com/supplier-4701497-survei...

    [6] https://www.instagram.com/cloudwalker_radar/

    [7] https://www.instagram.com/radar_lisa88/

    by kklisura
  • Sounds like a simple app with mic input being sent to a yamnet-like audio classification model for a single target detection. Hardly anything innovative?
    by k4rli
  • I wonder how this system can be protected from spam - if anyone can send data there, enemy can, too
    by tpolm
  • I feel like if/once they reach the number of expected participants (10k), it'd be easy to filter out the spam as long as the majority are truthful.
    by embedding-shape
  • If these Shahed drones have a propeller they should have a brutal signature between 0-250Hz as they are moving a lot of air. And if the engine speed of the Shahed stays constant it will be even easier to detect it ("Angry lawnmower sound".. but that's only the high frequency part of it).

    There are extremely sensitive differential pressure sensors (like SDP600-25Pa) available from Sensirion that aren't overly expensive.

    Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a tiny hole in it. This way the sensor will "Null" out the environmental pressure (which the bottle follows very very slowly) from both inputs. It then only will pick up everything high frequency which is left over (and the bottle cannot follow because of its small hole).

    This way I was able to detect washing machines that have a physical link to a house from many hundred meters (machine spinning -> house wall shaking -> pressure waves) away. The speed pattern of washing machines when spinning is very unique (several steps over many seconds).

    Add this with some GPS PPS frame timestamping and you should have a nice tracking network that doesn't require a lot of bandwidth. But maybe the setup must switch to analog differential pressure sensors as these Senirion-I2C sensors do not have a Sync ping for super precise timestamping.

    by MiracleRabbit
  • Doesn't wind fool this?
    by ShinyLeftPad
  • Interesting! I will like to see your circuits, if any.
    by ejanus
  • What’s the frequency response of that sensor? The datasheet says nothing.
    by amluto
  • Nice. And instead of smartphones, dedicated sensor using esp32 makes more sense imo.
    by dzhiurgis
  • The equivalent noise density of the sdp600 is 10^-2 Pa/sqrt(Hz). While the noise density of a typical microphone is 10^-6 Pa/sqrt(Hz). At same 50hz low frequencies. So either you're full of shit and a high quality microphone is x10000 more sensitive than this sdp600 sensor, or I'm not understanding what you're saying.
    by custardguy
  • Isn't detecting pressure waves in air exactly what microphones do?
    by stavros
  • Interesting! There are a lot of super loud cars in my urban area. I want to catalog where and when they drive, so I can stand on the side of the street and shake my cane at them.
    by Hnrobert42
  • > Use one differential side and connect it to a kitchen funnel for directional listening the other one to a plastic bottle with a very very small hole in it. It will pick up everything high frequency that's different to the environmental pressure.

    Nevermind drones, and war, that's all fine; but I need to know more about this. Is there a phrase or name for this I could use to find more information, maybe example schematics?

    by customguy
  • Or it is a public stunt? I am naysayer engineer. Build acoustic detection system for anomaly detection in manufacturing line. It worked with studio level equipment with lots of noise filtering measures. First challenge was to have microphone listening to the right place and getting reliable signal. Second challenge was to amplify the right signal to a level where the features could be extracted. I doubt an old android with dirty microphone can detect anything reliably.
    by lnsru
  • Shahed drones have increased in altitude from ~500m at the beginning of the Ukraine war to 2000-3000m, which is a 4x reduction in noise on the ground. The higher the drones are, the less noise they make at ground level, and the less effective this ground-based microphone system will be. The drones have moved to elevations to make them more difficult to target with ground based weapons. Reductions in ground noise are a secondary effect.

    The latest versions of Shahed can reach 5000m in altitude, which would largely be inaudible on the ground.

    by tristanj
  • So film the sky during charging and run a llm on it?
    by warumdarum
  • Could you simply use small cheap balloons with microphones to listen in higher altitudes? Or even small drones that carry the microphones with their own engine noise masked out?

    Edit: as others say, plain radar will suffice.

    by inglor_cz
  • > ~500m .. to 2000-3000m, which is a 4x reduction in noise on the ground.

    Radiative power drops by the square of the distance? Does anyone with a real physics background start demanding authority on a soapbox like this?

    by gnerd00
  • It's not about "can reach", it's fairly easy to get them to fly even higher. It's about danger of interceptors vs danger of detection. Today's Ukrainian detection network (based on radars) is so dense there is no way to hide from it anywhere, anyway, so high altitude wins.
    by anovikov
  • At those higher altitudes they are trivial for radar to detect, and from farther away too. They are adapting cheap commodity used marine radars to get this done in some places

    I suspect the Shaheds are going higher to mitigate AA ground fire. Higher up you have to send a missile or interceptor up.

    It’s a trade off.

    by dghlsakjg