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  xoa
  For a brief, beautiful moment from the headline I thought "oh good, more PoE sensors finally happening!" doho. But no not just about battery but any power at all, and an interesting approach for further research. Of course to actually get data from still requires powered devices but in a lot of cases it'd be much easier to have that be a single or small number of more easily placed central units vs every single sensor tag separately. Ultra low cost and simplicity are values all their own in terms of applications.My biggest immediately question though and one I'm a little surprised not see addressed, even at the research stage, is any mention of other animals. There is a bunch there about the ultrasonic frequency being well above the human limit of ~20 kHz. But IIRC for example dogs can hear up to like 45-60 kHz, and cats all the way to 65-85 kHz. I assume lots and lots of other animals also can perceive sounds well beyond human senses. Noise pollution is already a somewhat unrecognized but big problem for all sorts of life around us (not that it's irrelevant to human health either), so if more use of ultrasonics made that worse that's a concern. And as a practical matter the product market is probably going to shrink pretty dramatically if it drives pets mad, a lot of people have pets nowadays they care about a great deal. For that matter even in public environments if it messed with service dogs that might have ADA or equivalent implications.Still, good reminder of various side channels one doesn't always think about.
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  harg
  There already exists "kinetic" switches for lights etc whose switch contains some passive electronics that when actuated produces enough energy to emit a radio signal that can be read by a relay module. They're pretty handy as you can basically place the switch anywhere you want without the need for the wires to be there. The relay can live in the light fitting or somewhere else convenient.There's probably no reason why these kinetic switches can't also be used for detecting other events like doors opening/closing etc. I feel like a radio signal is a bit more reliable and easier to detect than high frequency sound.I also think calling these a "sensor" is a bit of a stretch. They detect events but have no knowledge of the current state of the thing they're sensing. E.g. the can detect a door opening/closing, but have no idea if the door is open or closed at a given time
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  anVlad11
  It's research, not a product. Even with that, framing it as a smart home sensor in the press release is a stretch.1) 93.75% success rate in controlled conditions, 92.1% in a somewhat-realistic deployment scenario - too low for reliability. I wouldn't use something like that to trigger smart home automations.2) Range hardcapped at ~1m due to how ultrasound works, you can't centralize detection. Their answer is to give everyone in the household a wearable receiver, which is eeeeeeeh idk, doesn't look consumer-friendly to me.3) Paper suggests a mix of durable and consumable parts for the transmitter. Their numbers show that the 3d-printed PLA cantilever needs to be replaced every 900 cycles or so. Should work fine, but...4) ...every transmitter pair needs to be tuned per-setup, every time. Not a plug&play in the consumer sense.
• inventor7777
  This is a neat idea.Personally, I would not find it useful as they seem relatively fragile and if the receiver is not bulletproof and VERY sensitive then it could miss state changes.However, it would be interesting to see how it would work if you were able to have different ones on different frequencies with one main receiver. That would make a cost effective way to track cabinets, doors, etc in the same room.
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  Zigurd
  My father was an engineer at Zenith when they were developing the Space Command TV remote control. This was a couple years before I was born, so by the time I got interested in hacking, Zenith TVs with this remote were commonplace. When visiting my friends homes I would prank them by jangling my keys and making the TV louder or quieter and randomly change channels. This presents new opportunities.
• superxpro12
  This is a very clever idea. However i think almost all smartphone microphone recorders cap out at 44.1khz or 48khz sample rate. Some have 96khz, but im not sure what is compatible with modern devices. That's going to limit how much frequency spectrum these fingerprints have to work with.
• PunchyHamster
  We've come full circle; one of first TV remotes used tuned pipes to generate sound driving the circuitry
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  itissid
  Wonderful. ultrasonic range emission having high S/N is amazing too. My hero usecase for this is to use these for behavioral therapy: Have a ring or a bracelet, thus without reaching for a phone or a notepad, record when a negative thought happens, i.e. a counter, or generate a sequence of ultrasonic sounds to map to specific kinds of thoughts. Have a sensor record and log them. I would then analyze the data across multiple days. My current method is recording them in obsidian.
• anon
  undefined
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  kumarvvr
  Would these maintain their signature under repeated use? Or regular wear and tear?
• NoSalt
  > "and cost only a few cents each"Now companies are desperately trying to figure out how to jack up the price to $10.00 each without us knowing they are ripping us off.
• tencentshill
  What about durability? They are mechanical metal pieces, so would eventually wear down or change tone.
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  chakintosh
  > ... and counting reps in the gymPeople need smart devices to count their reps !?
• anon
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• combocosmo
  It's a unique idea that I could see being useful in select situations. The reliance on wearable microphones sounds like a downside.Also I guess this might be annoying for pets that can hear well beyond 20 kHz.
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  tetris11
  Im not sure I got it. It generates acoustic signals and a microphone server picks them up.If so, will it penetrate through walls?
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  cyberax
  Trivia time! The first practical wireless remote control for TVs also used ultrasound: https://www.youtube.com/watch?v=MLPk1Us62xQ
• therealfigtree
  Titlegore
• mschuster91
  Interesting idea and reminds me of the German train security system PZB which acts completely electricity-free at the signal - a mechanical switch connects a capacitor to de-tune a magnetic resonance circuit, which is then detected by a passing train's magloop transmitter.Unfortunately... I see issues:> Those frequencies are above 20 kilohertz, which is the upper limit of sounds humans can hear.Yeah. Humans' range ends there, at least in adulthood. But what about pets? Wildlife? Children and toddlers? Or just people that take care of their hearing by not frying their ears with too much exposure to loudness? It's already an issue with "mosquito teenager repellant" devices.
• mystraline
  Where the profit in acoustic tuned sensors?Sensors must be using batteries, wear out in a month or so, tied to an oppressive cloud seevice, and regular up-sells of things that would be standard but we stratified types of paying users.For a dotedu, this is perfectly fine. But this wouldn't pass muster as a real product. You can't do all the HorribleUsesAsAService like almost all IoT hardware is.
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  ogig
  I can see some uses, but calling this system batteries free seems a stretch. A sensor is worth nothing if it can't be read, and to read this you need a powered microphone and computing. Some already common magnetic door systems do the same; door plate and magnet movement is enough to create a detectable current, (using no external power), then that signal is read and computed by an electronic/digital system (using power).