[HN Gopher] The Hummingbird Clock: date videos by background mai...
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The Hummingbird Clock: date videos by background mains hum
Author : wodow
Score : 382 points
Date : 2022-10-09 13:49 UTC (9 hours ago)
(HTM) web link (hummingbirdclock.info)
(TXT) w3m dump (hummingbirdclock.info)
| rajasimon wrote:
| I bet there was a movie or a documentary around this if anyone
| have the link please share it.
| barbazoo wrote:
| It's super shitty to just autoplay that sounds as soon as you
| open the page. Firefox on Android.
| chaosprint wrote:
| Interesting topic.
|
| I tried to mimic that sound design using Glicol but winded up
| getting something different.
|
| For those who are interested:
|
| 1. go to (https://glicol.org)
|
| 2. run the following code:
|
| // ----------------
|
| o: sin ~freq >> mul 0.5;
|
| ~freq: sin 0.2 >> mul ~range >> add 50;
|
| ~range: sin 0.4 >> mul 1 >> add 2;
|
| // ----------------
|
| 3. tweak the numbers to get different sound
| manv1 wrote:
| This is so fucking cool.
| kzrdude wrote:
| Just curious, are there any software hacks (not audio/video at
| all) that use any aspect of mains hum for say info leakage?
| (Could be impossible.)
| GranPC wrote:
| How does this auto-play sound without user interaction?
| s0rce wrote:
| It didn't for me on Chrome on OS X. I had to click one of the
| links before the sound played.
| kevingadd wrote:
| Synthesized sound (AudioContext) works a bit differently from
| playing videos/sound files in the web permissions model, for
| whatever reason. IIRC Chrome and Firefox both treat various
| forms of interaction as an OK to synthesize audio, so your
| browser probably decided you had met that criteria.
|
| Chrome has a list of special websites that are given that
| access automatically, though I doubt this website is on that
| list...
| GranPC wrote:
| Very interesting. I'm using Firefox and it started playing
| immediately when I switched to the tab. Thank you for the
| details!
| etaioinshrdlu wrote:
| I have never heard mains hum as wobbly as on this site. It seems
| exaggerated.
| IshKebab wrote:
| It's not real. It's obviously too high pitched.
| rtanks wrote:
| The sound is very aggravating.
| ctxc wrote:
| Exactly. Although it _is_ interesting, was not expecting auto-
| play.
| atoav wrote:
| Time to get your own isolated grid huh? Maybe with solar and
| inverters?
| [deleted]
| pugworthy wrote:
| To what end? What do you want to obfuscate by doing this?
| coldtea wrote:
| https://www.aclu.org/news/national-security/you-may-have-
| not....
| pugworthy wrote:
| That's not really an answer beyond "Because FUD".
|
| FWIW, I've been an ACLU member for quite some time.
| ris wrote:
| Probably better to run a decoy signal (or two) in the
| background with similar characteristics.
| s0rce wrote:
| You'd need to make sure there is no grid nearby. If you were
| completely off-grid and away from power lines or anything then
| you'd have no signal at the mains frequency. Certainly
| possible. Probably easier to just use a filter to mask the
| frequency component.
| ratww wrote:
| An on-line UPS like those used in datacenters or music studios
| is probably enough. They basically have rectifiers and
| inverters in them.
|
| Some of them have phase-locked loops to sync the output
| frequency with the mains, but probably won't stray as far from
| 50Hz (or 60Hz) as the mains themselves seem to do. If they do,
| unplugging the mains and using the battery is probably enough
| to get pure 50Hz back!
| jsjohnst wrote:
| > An on-line UPS like those used in datacenters or music
| studios is probably enough.
|
| Only if you don't have mains power anywhere near the
| recording device. You don't need to be plugged into mains
| power to have it be present in a recording.
| ratww wrote:
| True! And that applies for every case. Even if you have
| 100% isolated mains with solar or battery, you'll get 50hz
| from neighbours (especially apartments) and power lines
| close by.
|
| I remember having this issue when working in a recording
| studio during college, even when we switched to battery and
| turn the mains off, we'd still get hum in some guitars.
|
| Funny enough I was recently reading an interview with
| producer Michael Beinhorn and he mentioned having some
| "mystery EMF/RFI event" happening in New York around 1997,
| coming from a specific block, and he had to relocate a
| recording session to Los Angeles because of how strong it
| was interfering with the guitar amps and other equipment
| [1].
|
| [1]
| https://gearspace.com/board/interviews/1385579-interview-
| mic...
| jsjohnst wrote:
| I really wish this story included which half block area
| it was strongest.
| ratww wrote:
| That would be very interesting to know! Especially
| considering the two studios he mentioned aren't exactly
| close to each other:
|
| https://goo.gl/maps/MLw3twvRi9GumYeX8
| ok123456 wrote:
| Filtering out 50Hz/60Hz noise as a band stop filter is a common
| audio post processing step, precisely because it's noise from the
| power system.
|
| I wouldn't be surprised if there were phones that automatically
| applied this filter.
| FPGAhacker wrote:
| Your point still stands but the noise here is effectively a
| higher frequency modulation of the base AC oscillation.
|
| In other words, the base oscillation of 50 or 60 Hz is not
| stable, but instead varies a little above and a little below at
| higher rates.
|
| The magnitude is significantly lower than the base mains
| frequency. So possibly not audible above any other noise in the
| recording, but present nonetheless.
| ok123456 wrote:
| These filters will take that into account since it never has
| exactly been 50/60Hz. It's just the expected mean.
|
| Maybe it's present in subsequent harmonics (e.g.,
| 100/150/200Hz for 50Hz) as a systematic deviation from
| additive white noise. But, this would be difficult in
| practice to reliably isolate these signals via some form of
| component analysis.
| paulkrush wrote:
| How far do I or can I transmit into the grid? How far do load
| changes from my house transfer into the grid? Surely my neighbors
| could detect 1us spikes not big enough to pop mains at say 800hz?
| ratww wrote:
| I remember consumer devices from the 80s that allowed
| transmitting audio using mains. They were already outdated by
| the time I saw them in the 2000s.
|
| Me and some friends tested them and tried transmitting to a
| neighbours house (connected to the same electrical post) and
| had no success at all. There was just too much noise, coming
| from other houses. However with digital technology I'm sure you
| can get a much better range.
| mastax wrote:
| Things like HomePlug GreenPHY are used for smart meters. (Also
| electric car charging for some inexplicable reason) I don't
| know how they're typically deployed but I'd think at least a
| few miles? It wouldn't make much sense to use if you'd have to
| have the receiver really close - just use wireless.
| Shish2k wrote:
| Using ethernet-over-powerlines within my house, different
| circuits within the same building have trouble talking to each
| other, so I wouldn't recommend that for cross-building
| communications...
| h2odragon wrote:
| There were some small, low power AM radio stations that
| "transmitted" via power grid in mountain towns in North
| Carolina, a while back. I've been told that they had real
| trouble getting through transformers and they were using the
| main distribution lines and broadcast AM frequencies. That's
| with decent levels of power applied.
|
| I expect the incidental signals your usage generates are going
| to be hard to detect past your power meter and almost certainly
| un-resolvable past the distribution step down transformer.
| JohnJamesRambo wrote:
| This is absolutely fascinating.
| gugagore wrote:
| What I don't understand is how much technique assumes of the
| local oscillators on the recording device, which also vary.
| jsjohnst wrote:
| I don't see how this can be used to "authenticate" a video. If
| I'm already editing the video anyway, could you filter the
| original hum out and replace it with the correct frequency for
| the time you wanted to fake? There's got to be a margin of error
| anyway, so would seem very possible to fake unless I'm missing
| something.
| helsinkiandrew wrote:
| Yes, in the same way you could leave fake fingerprints and DNA
| at a crime scene.
|
| This was used in a court case in the UK where the defence
| claimed the police had tampered with a recording - editing
| together separate recordings into a single one to make their
| case. An academic 'expert' analysed the recording and
| corroborated the claimed recording times and the accused were
| found guilty.
| twawaaay wrote:
| You could. The point is to disprove the validity of the video.
| Correct signature is not a proof the video is valid but
| incorrect one could be proof that it is not.
|
| In practice, most people who manufactured videos before very
| recently were simply unaware of this possibility. I learned
| about it many years ago but I still forgot about it and
| probably would not try to do anything about it if I was
| manufacturing a video.
| mastax wrote:
| Only if you know to do that. Nothing is ever 100%.
| kadoban wrote:
| You can use it as evidence either way, especially evidence that
| something is _not_ genuine. It's not proof though.
| braingenious wrote:
| This is fascinating. Does anyone know if this phenomenon is
| unique to Britain? I wonder if this could be replicated in other
| countries.
| LinuxBender wrote:
| Interesting. What effect if any will my home being entirely on
| off-grid inverter 100% of the time have on this? I use
| Solar/Commercial/Generator -> DC Power Supplies / Charge
| Controllers -> Inverter -> Non-Resistive loads. My inverters are
| entirely isolated from commercial power. Can someone perhaps tell
| the make/model of my inverter?
| alexvoda wrote:
| I guess it depends on how far you are from mains electricity
| infrastructure.
| spoonjim wrote:
| Seems like you wouldn't need to actually record and store the
| mains hum... you could just extract it from other videos with
| known datestamps.
| IshKebab wrote:
| Definitely wouldn't work. You'd be matching two very noisy
| signals instead of one clean and one noisy one (which already
| requires a long time period to match), and it would be really
| hard to get enough videos to cover all time and then why would
| you bother when recording the hum directly is easier and
| better?
| beardyw wrote:
| And then add it to your newly made black and white video tape.
| Forgery 2022.
| sbf501 wrote:
| Except for the 10 other techniques we _don 't_ know about.
| Did you know about this before the HN post (or original post
| from 2021)? I sure didn't, which means there are other tricks
| hiding out there.
| coldtea wrote:
| you might have not, but many did
| beardyw wrote:
| I didn't.
| paulkrush wrote:
| Fun fact: You can hear the harmonics of the grid and IP switching
| if you open the site in two separate browser windows.
| matja wrote:
| Fun fact: The source contains: rand = (Math.floor(Math.random()
| * 3) - 1); vco.frequency.value += rand * hum_delta;
| zxcvgm wrote:
| Tom Scott did a video about this topic in 2021:
| https://www.youtube.com/watch?v=e0elNU0iOMY
| Karellen wrote:
| That's weird.
|
| I came here to check that someone had linked to that video, but
| in my mind it feels a lot longer ago than Dec 2021. I feel like
| that video should be 3 or 4 years old.
|
| It's doubly weird because that normally happens the other way
| around, where I think something happened about a year ago, and
| it was actually 3 or 4 years ago. Or I think something happened
| 5 years ago, and it was actually 10-12.
| Smoosh wrote:
| People seem to be reporting anecdotally that the pandemic has
| messed with their sense of time. I wonder if there are any
| serious research projects underway to study this phenomenon.
| curl-up wrote:
| I would have said 3-4 years as well, and I would have been
| certain beyond any doubt that it was more than 2 years.
| Crazy.
| ratww wrote:
| I find it personally hard to date stuff that came out or that
| I watched during the pandemic. To me it felt like I consumed
| 4 or 5 years of content in the span of each year. My sense of
| time is completely twisted.
| djmips wrote:
| Maybe you should submit the video to The Hummingbird Clock
| and find out for sure! hehe
| Aachen wrote:
| In 2018, we went with school to the national forensics
| institute where they (among other things) presented their
| research on this. Not sure if it's also online somewhere; their
| website is nfi.nl
| helsinkiandrew wrote:
| This 5 minute video from Tom Scott on YouTube is a good overview
| without that annoying hum:
|
| https://www.youtube.com/watch?v=e0elNU0iOMY
| sandworm101 wrote:
| How many videos, outside fixed webcams, come from devices plugged
| into the wall? I venture that 99.99% of videos where the
| timestamp is questionable come from battery-powered devices. As
| for mains hum, portable devices pick up so many hums from so many
| sources that i doubt much useful mains hum is ever recorded.
| nippoo wrote:
| Mains hum is by far the most powerful source of electromagnetic
| radiation in most indoor places. And the device doesn't have to
| be connected to the mains to pick up EMI from it - turn up the
| gain on any battery-powered preamp and you'll hear it.
| lalopalota wrote:
| If you follow the "How it works" link:
|
| > Digital recordings almost always have mains hum on them,
| either because the device was plugged in to the mains or
| because it inducts it off nearby cables, lights and
| appliances in a room.
| dev_tty01 wrote:
| This is why guitars often use a humbucker pickup to cancel
| the EMI from the mains.
|
| https://en.wikipedia.org/wiki/Humbucker
| s0rce wrote:
| You don't pick up the hum from being plugged into the mains.
| Nearby equipment generates sound at the frequency (and
| harmonics) which are picked up by the microphone. Various other
| equipment is sensitive to the EMF. As others mentioned its
| pervasive indoors and near power lines.
| pugworthy wrote:
| That clock graph is fantastic.
|
| I haven't let it run long enough to see if the minute and hour
| hands do the same line, but if so what a great way to show
| minute, hour, and day (24 hour clock) trends.
| evan_ wrote:
| This would be good to use for syncing clips from multiple cameras
| in video editing packages
| Phenomenit wrote:
| I think this is useful in many ways, I hope one can get access
| or build one.
| anfractuosity wrote:
| I'm surprised when it says "the exact same buzz can be heard at
| the exact same moment nationwide from Land's End to John o'
| Groats", I didn't realise it would be the same across the UK.
|
| I played a little with a transformer to take 230VAC -> 12VAC, and
| then using a potentiometer to feed the waveform into a soundcard.
| But I'm not sure the sample rate of the soundcard was high enough
| to accurately measure the times between 0 crossings.
|
| Photo of the very messy setup -
| https://www.anfractuosity.com/files/hum.jpg
| sgtnoodle wrote:
| Explicitly watching for zero crossing seems like a rather
| limiting approach to quantifying a sine wave. Even then, at
| 48Khz you should get 400 samples between zero crossings, so you
| should do better than 0.5% accuracy.
|
| There's a lot of information held within the time series data
| of an audio signal, and something like an FFT can tap into it.
| For a 60Hz signal the Nyquist frequency is 120Hz, which is well
| below any audio interface. It seems like accuracy of any
| processing would be limited by a crystal oscillator somewhere
| more than anything, and perhaps any unintentional signal
| aliasing if there's no low pass filter before the audio
| interface's ADC.
| im3w1l wrote:
| Well 60/50Hz isn't the only relevant frequency here. Lets say
| you plug in ethernet-over-power (available off the shelf).
| You'd need a very fast interface to notice that.
| sgtnoodle wrote:
| I can't imagine folks' ethernet-over-power signals are
| propagating across the national power grid, and even if
| they were, they aren't getting picked up in any audio
| streams.
| anfractuosity wrote:
| That's a good point re. the crystal oscillator.
|
| Maybe I'm wrong re. the sample rate then, I found this paper
| - http://www.forensic.to/ENF%20processed.pdf , where they
| mentioned 8kHz as the sample rate.
|
| I think what I was thinking is commercial systems such as
| https://synectic.co.uk/product/sd037-frequency-monitor-html/
| mention specs such as 'The frequency monitor units are
| supplied pre-calibrated to an accuracy of +/-0.0001Hz'
| sgtnoodle wrote:
| I was mainly responding to the hobby experiment of
| connecting a 12V transformer to an audio input on a
| computer.
|
| Even then, it seems like 8Khz sampling would be plenty to
| fingerprint a 60Hz signal. 8Khz sampling can capture
| information up to 4Khz, per the Nyquist frequency.
|
| That frequency monitor spec sheet mentions 90ms response
| and filtering, which would imply it averages information
| across 5 periods. Also, because it's a purpose built
| device, it's likely not periodically sampling the waveform
| with an ADC, but rather has a dedicated zero-crossing
| detection circuit that feeds into a capture input on a
| digital timer with at least microsecond resolution.
| quacksilver wrote:
| This is widely known and allegedly used by law enforcement
| forensics etc.
|
| I have often thought about building a SaaS service that strips or
| adds the correct hum and harmonics to videos if you wanted to
| plant some false evidence or make a good deepfake. If it failed
| to make much cash I could put it on github for free.
|
| I have never quite found the time and openly doing that kind of
| thing is probably likely to attract undesirable attention.
| agilob wrote:
| >If it failed to make much cash I could put it on github for
| free.
|
| Silk road was closed in 2013
| alexeldeib wrote:
| Markets are alive and well. Not as prolific, but not dead.
|
| Not really sure what your point is, though? They don't
| typically have audio recordings so not sure I see the
| relevance.
| unvs wrote:
| There's an artist called Oystein Wyller Odden that works with
| mains hum. I find it pretty fascinating:
|
| _Kraftbalanse is a musical translation of the hum from the
| mains; i. e. the frequency of the alternating current. The piece
| is based on the fact that this frequency is not stable, it
| fluctuates subtly around 50 Hz as a direct result of supply and
| demand in the power market._
|
| _The composition consists of a self-resonating piano that is
| tuned to resonate on 50 hz and overtones of 50 hz (100 Hz, 150
| Hz, 200 Hz etc.) The piano is fitted with vibration-elements -
| transducers - plugged directly into the electrical grid, causing
| the resonance and timbre of the piano to change with the
| fluctuations on the power market._
|
| _The piano is accompanied by a string octet. The musicians are
| equipped with voltmeters that measure the frequency of the
| current in real time, as well as a score of instructions on how
| to respond to changes in this frequency._
|
| https://vimeo.com/370554138
| Waterluvian wrote:
| I was expecting one of those music YouTubes where they take
| some sample and process it so much that it doesn't really
| matter what the sample even was. But I'm pleasantly shocked
| (ha!)
|
| They really evoke the feeling of electricity. It reminded me of
| the soundtrack to the Chernobyl miniseries. It's... powerful
| and eerie and calmly, effortlessly, sluggishly intimidating.
| huehehue wrote:
| This is awesome. I've been kicking around the idea of a
| notation/composition system that uses external forces
| (temperature, moon phase, time, etc) as live input but prior
| research is a bit hard to come by.
|
| Feeding signal into e.g. a guitar pedal is easy enough, but
| mutating an entire orchestra in real time is a different beast.
| If anyone knows of similar works I'd be grateful for links.
| rzzzt wrote:
| You can also hear it around 3:00 and towards the end, while the
| artist talks about the work: https://youtu.be/I_BanULj8wk
| mechanical_bear wrote:
| Ugh. Login to watch. Hard no. Too bad, seems interesting.
| sillysaurusx wrote:
| Odd, I was able to watch it without logging in. (It is!)
| Retr0id wrote:
| I wonder if it's based on geolocation. I'm being forced to
| log in, in the UK. I've noticed sites increasingly doing
| this to UK audiences, despite the fact that, iiuc, the
| draconian age-gate legislation hasn't actually landed yet.
| taejavu wrote:
| Umm, I simply ignored the "log in with Google" popup and
| clicked play. Does that not work for you?
| Retr0id wrote:
| > Video is not rated. Log in to watch.
| tgsovlerkhgsel wrote:
| I was excited to possibly see this provided as an open source
| tool or at least an automated service, but the site offers a form
| to request dating, which looks like a manual process. That's not
| really making it available to everyone.
| IshKebab wrote:
| Yeah it's kind of surprising that nobody has set up a properly
| open one with downloadable history. This "fill in a form" one
| is lame.
| mike_hock wrote:
| It's super fishy. Why should I trust them to process
| potentially sensitive material? If you want to level the
| playing field, just put the collected data out in the open so
| anyone can download it and correlate any video they like with
| it, no need to upload the video to Mr. Anonymous and hope he's
| being truthful about his pure and noble intentions to support
| human rights.
| remram wrote:
| How difficult would it be to defeat that completely or fake a
| different date? If people can find subtle noise that fools
| computer vision algorithms, can something similar not be applied
| to this?
|
| A band-pass filter might be a little simplistic because it's
| never 100% attenuated and the harmonics persist, so given a long
| enough sample you would probably be able to correlate. But
| perhaps more advanced techniques exist, if you know exactly what
| the other party is looking for?
| sholladay wrote:
| Yet another reason that the world's electric grids should be
| replaced with DC power.
|
| AC power was only a good idea when we didn't know how to make
| good DC-to-DC voltage converters.
|
| https://www.electricaltechnology.org/2020/06/advantages-of-h...
| KMnO4 wrote:
| Or when we decided to live more than 100m away from the power
| plant? DC doesn't travel well.
| Aachen wrote:
| Warning: site autoplays a loud (presumably 50Hz) buzz...
| bumpty wrote:
| According to http://hummingbirdclock.info/static/js/hum.js the
| base frequency is 200 Hz, but has a gain of 4, which seems to
| push it more into the higher harmonic range as the waveform is
| clipped: // hum.js // toggle
| html audio on/off // with cookie to maintain state
| // and use html5 audio synthesis // ios html5 audio
| must be triggered // call init_hum() after DOM loaded
| // 0. create audio context // 1. create oscillator,
| define // 2. connect oscillator to gain // 3.
| create gain // 4. connect gain to output // 5.
| start oscillator (on click) var audio;
| var audio_context; var control; var vco, vca;
| var hum_delta = 1; var hum_base = 200; var
| hum_min = 100; var hum_max = 400; /*
| init */ function init_hum() {
| audio = get_cookie("audio"); console.log("audio = "
| + audio); audio_context = get_audio_context();
| console.log("audio_context = " + audio_context);
| control = get_control(); if (audio_context !=
| "false") { if (audio != "off") {
| set_hum(); hum_on(); }
| } else { set_cookie("audio", "off");
| } } function get_audio_context() {
| var which_audio_context = window.AudioContext || // default
| window.webkitAudioContext || // safari
| false; this_audio_context = new
| which_audio_context; return this_audio_context;
| } function get_control() { var
| this_control = document.getElementById("control");
| this_control.addEventListener("click", hum_on_off);
| return this_control; } function
| set_hum() { vco = audio_context.createOscillator();
| vco.type = 'sine'; vco.frequency.value = hum_base;
| vca = audio_context.createGain(); vca.gain.value =
| 4.0; vco.connect(vca);
| vca.connect(audio_context.destination); }
| /* on off */ function hum_on() {
| set_hum(); vco.start(0);
| control.innerHTML="×"; set_cookie("audio",
| "on"); audio = get_cookie("audio");
| console.log("audio = " + audio); }
| function hum_off() { vco.stop(0);
| control.innerHTML="+"; set_cookie("audio", "off");
| audio = get_cookie("audio"); console.log("audio = "
| + audio); cleanup(); }
| function hum_on_off() { if (audio == "off")
| hum_on(); else hum_off(); }
| function cleanup() { vco.disconnect(0); }
| /* cookies */ function set_cookie(cname,
| cvalue) { document.cookie = cname + "=" + cvalue;
| } function get_cookie(cname) { var
| name = cname + "="; var ca =
| document.cookie.split(';'); for(var i = 0; i
| <ca.length; i++) { var c = ca[i];
| while (c.charAt(0)==' ') c =
| c.substring(1); if (c.indexOf(name) == 0)
| return c.substring(name.length,c.length); }
| return ""; } function
| check_cookie(cname) { if (getCookie(cname) != "")
| return true; else return false;
| }
|
| The audio spectrum analyzer on my phone (Spectroid) records it
| most strongly around 1000 Hz.
| jeffbee wrote:
| At 50Hz it would be inaudible on most computers.
|
| https://szynalski.com/tone#50,v1
| tiborsaas wrote:
| True, but cheating a bit with a triangle wave would solve
| it thanks to the harmonics.
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(page generated 2022-10-09 23:00 UTC)