What is the mysterious 'global Hum' and is it simply noise pollution? (2019) | Hacker News Reader

What is the mysterious 'global Hum' and is it simply noise pollution? (2019)

theguardian.com

67 pointszeristor80 comments

It's an interesting story but the whole investigation seems rather slipshod.

> “The bulk of the evidence suggests that the Hum is not an acoustic sound.” He explained: “This is indicated by the simple fact that most people do not hear it.”

Surely it would be trivial to set up a sensitive microphone, record some samples when a "hum-hearer" says it's happening, and analyze the frequency spectrum? Instead they're just guessing that it's RF-related... but then the article goes on to discuss a bunch of sources of low frequency acoustic noise?

> For instance, multiple Hum hearers, if in the same room together, will match the Hum to different acoustic frequencies. “That never, ever happens with standard acoustic sources, of any frequency. It just simply never happens,” he says.

If only we had some kind of machine that could objectively measure acoustic frequencies...

If it were high pitched, we'd write it off as tinnitus. If there's no low-pitched equivalent (is there?) then it's probably just a sampling of people who live within a block or two of someone with a high-powered subwoofer on their stereo.

> If there's no low-pitched equivalent (is there?)

There is indeed low-pitch tinnitus. It's much less common. I have a version of it. In complete silence, I "hear" a rather pure 73 Hz tone. Luckily I am rarely in complete silence, or I think it would drive me crazy. A doctor said that I perhaps have inner ear damage that my brain has compensated for. I've had it for about a year.

This is the tone: https://www.szynalski.com/tone-generator/#D2,v1

Wow, that must be really annoying. I have it at a very high pitch.

I did get it checked out, and inner ear or nerve damage was suggested as a cause. However, they also suggested that poor posture putting strain on the muscles around the neck could also be a factor, and I have noticed it gets worse when I slouch for extended periods. If you haven't investigated this side of things, it might be worth a go.

I was thinking that the 73 Hz tone is rather pleasant compared to the ~13kHz tone I hear/perceive in both ears almost constantly. It used to bother me a lot, now I accept its presence and try to focus on things I'm doing instead. Of course there's no knowing what the 73Hz experience is like when sustained. My high-pitched tone I attribute to a combination of exposure to loud live music and hypertension from coffee (and to a lesser extent alcohol). The intensity and pitch does vary and often something will trigger the start of the tone in the morning, like the sound of the towel hitting my ears when drying my hair. I've recently cut down my coffee intake dramatically.

I think I agree with you. The low D note I hear must be more pleasant than the 13kHz you hear.

I've heard something similar for the past two years, except mine is at 78 Hz, and only in my left ear. As with you, I hear it only when it is extremely quiet. When the room ambient noise is above about 35 dBA, I never hear it.

Also, oddly, it comes and goes over a scale of months, seemingly at random. One day, I'll wake up in my quiet bedroom and hear it, and I'll continue to hear it in quiet environments for a month or two. Then, after those several months, I'll wake up again and find it gone.

I notice a very loose correlation to it abating after a loud weekend, like a weekend spent driving my race car or doing metal fabrication, but otherwise it seems random.

A while back I ran it down with medical professionals, but the gist of that expensive adventure was that it was likely idiopathic. It appears to be of the subjective type rather than objective, but -- long story short -- that's not definitive.

My "solution" for now is to run the ceiling fan at night during the months it's present.

Very similar experience, after a bit of research it was clear the 'global hum' explanation loses out to the much simpler explanation that it's an internal effect.

I too found exposure to loud noise supressed it (e.g. regularly suppressed for a couple of days after nightclubbing), also only 'audible' in very quiet surroundings (even lightly touching an earlobe caused the 'hum' to cut out).

It went away after life got noisier (kids'n'dogs).

How do you know that's the frequency what you hear? Is it because when you add more 73Hz you don't notice it as much as adding other frequencies?

Other nearby tones will sound "out of tune". At least that's how I can find the pitch of my tinnitus.

I "hear" the tone clearly. From that, I found this online tone generator, and experimented until it sounded nearly exactly like what I hear. I grew up around a lot of music, so maybe it's easier for me to pick out a tone.

I have experienced this after a long noisy drive and big change in elevation. For me, was closer to 50 60hz.

How do you know the frequency of what you hear? Is it a guess or measurement?

Another person asked this too. There's obviously no way to directly measure it, since it is simply a perception of something that does not actually exist. I only "hear" it because I have either neurological damage or inner ear damage. But I know musical notes, and it's a D2. A C#2 is too low, and a D#2 is way too high. It might be more like a 72Hz instead of 73Hz (D2), but it's close. It's a "guess" in the same way that any singer might sing any other particular note. I can hum it, in tune with itself, although the sound of my own voice destroys the perception. I can use that tone generator I linked above, starting it and stopping it, and compare until I hit the right note. Just like tuning a guitar by ear. I do have to have absolute quiet to hear it, but I can reliably hear it 100% of the time when in absolute quiet.

I've heard a low pitched 'hum' for a couple of years now at my house. It is weird because it actually has two tones, one at ~28hz and one at ~36hz and it alternates between them...usually at the lower frequency but will sometimes hop up to the higher frequency for a few seconds.

I've tried recording it with several different high quality microphone setups and absolutely nothing at all. Also, nobody in the house and none of my neighbors hear it. So at this point I think it's something in my head, but I only hear it when I'm in my house. Never when I'm on the road.

Not sure if this counts as 'the hum' but it's definitely weird.

Perhaps you've already considered this, but could it be caused by a fan or some other source of mechanical vibration in your house? Acoustic propagation within a house can be surprisingly complicated.

Some years ago I noticed a very strange hum in one corner of my basement. Thanks to funky acoustics, I couldn't identify the source for a while, but IIRC it ended up being a fan in another part of the house. I suspect most of the energy traveled through the house framing, and ended up resonating in the room I was in at the time.

It’s very possible. There’s another source of noise that I’ve noticed, it’s qualitatively different so I don’t think it’s related, but there is a life flight helicopter pad about 2 miles from me. Every now and then there will be a real low rumble in the house that you can actually feel more than hear. About a minute later the helicopter will fly overhead.

There is an auto assembly plant about 5 miles away, if it’s not in my head it’s almost certainly something from there. The ground here has a extremely high clay content, and when you get down a bit it’s like one solid mass. It seems ideal for transmitting sound long distances.

If you have enough time when you notice the sound, it might be interesting to turn off your house's main circuit breaker to see if the sound goes away. Might be a quick way to bisect the analysis.

Ah! Now that you mention it, I have done that. It didn’t make a difference and I think that is roughly when I started seriously considering this was all in my head.

I can see why that possibility would drive you nuts!

Then I second the idea of getting two recordings (baseline and when you hear this) using a suitable mic. If you can afford the hardware, it's got to be way cheaper than questioning your hearing and/or psyche for the rest of your life :)

Definitely worth trying! Thanks for the ideas and the support, 2020 isn't the best year for 'hearing weird things at home' haha :)

Glad to be a sounding board. Yeah, 2020 is definitely the year we could write the book, "Gaslighting Yourself for Dummies". Best of luck :)

Perhaps you could clamp a microphone to a metal rod stuck into the Earth to test that hypothesis.

Same for clamping onto the structure of your house for the vibration/fan one?

Finally, if all else fails, clamp a microphone to your head

I could hear a fait beeping in one corner of my kitchen, but if I moved ~3 feet in any direction it disappeared.

Eventually discovered that it was some kind of acoustical beat frequency from the motor noise in the refrigerator reflecting off the back wall. Moved the refrigerator ~1 inch further away from the wall and the sound disappeared (at least from the location I had been able to hear it)

I heard an annoying hum out in the wilderness of Charlo MT that nobody else could hear, but chalked it up to radio equipment because there WAS actually a large tower nearby, that could be explained as part of a hi-def video streaming operation to capture these lovelies, just "next door" aka within a few miles.

Charlo Osprey Cam: https://explore.org/livecams/ospreys/charlo-montana-osprey-n...

I assumed there was some heavy duty radio equipment to handle this but was never really able to confirm the source of the noise, I was visiting for a couple of months two years ago. There were days when I just could not tune it out, and there were days when I either didn't notice it at all, or it wasn't present.

Towers can generate noise all by themselves in moving air through vortex shedding.

How do you know the frequencies they're at? Did you Match it with sounds from your computer?

What constitutes high quality microphones for you? Where these microphones that were made for this low frequency range?

EDIT: Especially on the microphones maybe the actual noise isn't 28Hz, but the 28Hz are harmonics of a 14Hz, 7Hz, 3.5Hz,... vibration. These harmonics may get produced inside some structures near your ear, explaining why you hear it and others don't.

You'd need special equipment to measure these low frequency vibrations.

Yes matching sounds on the computer. I can actually hear a beat when they are close but not exact.

Mics were a variety of xlr and usb from rode, sennheiser and yeti over the past few years. Definitely in the frequency range but only moderate sensitivity at that freq and low to moderate self noise. Not exactly scientific but I would expect to see a bump of energy in the spectrum and get nothing.

Yeah you'd need PCB mics with reference level sensitivity. They cost over 800$ and the equipment that measures the noise costs in thousands.

I'd be really intrigued whether you can find something at the harmonics using an infrasound microphone (some can measure down to 0.1Hz), but the price is probably prohibitive for an experiment.

Saw some interesting research on using infrasound to locate elephants. they managed to come up with something that was about $9 in parts including microphone. (Plus a SBC for analysis).

A bit of searching lead to some DIY stuff using subwoofers (speakers) as the microphone input then some low-pass filtering and then fed to an op-amp.

Here's the link to the research paper on the elephant detector https://www.researchgate.net/publication/320596116_Eloc_Loca...

That's the next step, just have some other projects to get out of the way first. There's a fairly low cost infrasound recording option using loudspeakers[1] that I think is worth a try. I'm also interested in building a seismograph, which might be able to pick it up on the high end of its range. If the sound is anywhere as loud as I hear it, there isn't much need for anything ultra-sensitive.

[1] https://www.youtube.com/watch?v=mekmsgjSqR4

I actually plan on recording sounds from my head, too. Could be weird spasms or something causing it, the lack of any variation in the two pitches makes that seem unlikely but possible.

They might be able to do it with an Earthworks M30 measurement mic, which claims accuracy down to 3 Hz, and an appropriate digitizer. It's expensive but not as blisteringly expensive as lab mics like Brüel & Kjær's gear.

I wonder if fans with (not a power of 2) blades could also generate surprising tonal (i.e., not transient) frequencies.

I could imagine this logic also applying to other pumps in the house: AC pumps, baseboard heat circulators, sump pumps, etc.

I heard this weird hum in what I would judge as similar frequency band to yours when I stayed at my sisters new house. The thought that I have a weird new ear problem or something really freaked me out at first. And then I realized that I'm only sleeping on a thin mattress directly on the floor and they have a water circulating under floor heating there that just created this hum.

There is simply no way they forgot microphones exist. The obvious conclusion then is they did try microphones, detected nothing with them, then decided not to report this negative result.

Yes you're absolutely right. I work in NVH dept at one of the car companies. We measure interior noise using mics which are accurate starting from below 20 Hz to 20 kHz. So this should be very trivial.

One of the frustrating things about "the hum" that the article mentions is that, academically, it's been lumped into the lunatic fringe of conspiracy theories, and serious scientists aren't interested. It does seem like the right equipment and expertise should pretty easily be able to determine, conclusively, whether or not any given "hum" is a real physical sound.

In one of my old apartments, I was able to hear modulating pure tone low frequency noise on some nights. I definitely could tell the noise was perceptible only during night. I think there could be many reasons for this noise from water filtration plants, power plants, to any other large industrial applications.

I was curious to see if it might be related to something called Schumann resonances since there are three harmonics that fall in to the range of human hearing at 20.8, 27.3 and 33.8 Hz [1].

I doubt that it would ever be strong enough to be perceived by the human ear but if the ionosphere can act as a wave-guide at those frequencies (20 and 40 Hz) then a fairly distant but loud noise could conceivably 'bounce' the sound hundreds or thousands of miles and 'hearing' it would depend on a) being at the exact location that the sound wave bounced down, b) ideal atmospheric conditions, c) being able to hear low frequency sounds and or d) having something inside a house that develops a sympathetic resonance.

Slightly plausible but highly unlikely but it did lead me to https://en.wikipedia.org/wiki/List_of_unexplained_sounds which made the thought experiment worthwhile.

[1] https://en.wikipedia.org/wiki/Schumann_resonances

Sometimes it's just boring industrial noise pollution. https://www.npr.org/2020/08/04/898853311/it-took-a-pandemic-...

I wonder whether people heard the hum more or less, quieter or louder during the lockdown when everything was so much quieter. Anyone know of any change?

I've heard the hum many times in different parts of the UK and its usually loudest on bank holidays - that is, the days when things are most quiet. I think I'm hearing my own blood pumping away - a kind of merged drum beat.

Now - I have also heard the associated "Hummadruz" too - which is more of an insect / bee drone. I recorded it on my camera but the audio couldn't pick it up. However I was walking though a field where there were many foxgloves, dry stone walls and bees around in high summer. Non hive bees will often live and buzz in their holes, so the hummadruz could be literally insects.

The low bassy drone in both the hum and the hummadruz makes it hard to pin point the direction - it's why you only need one bass speaker in most hi fi systems.

> Now - I have also heard the associated "Hummadruz" too - which is more of an insect / bee drone.

I hate mosquitoes, but mainly their sound. Sometimes when it's pretty silent, I can hear mosquito like it was in a room (with pitch varied like real mosquitoes) but it's entirely in my head (like tinnitus, I have it sometimes when air pressure changes), I found out when I've tried to cover my ears and sound didn't stop. I've already already learned to distinguish between real ones, imaginary ones and TIR's on nearby road (which simetimes sound similar).

I started hearing a hum in March, coinciding perfectly with my shift to working from home during lockdown. Glen MacPherson (who runs the hum database) has also reported a surge in hum reports.

I have dealt with hearing a Hum and it is super frustrating.

Near the end of my time living in Seattle, something started making a hum. It was loud, and deep, and penetrating. Miserably loud - and yet my SO, who was visiting the day it started, heard nothing. I went on a trip the next day and it persisted for a while in my head, but stopped the next morning, and I spent a hum-free weekend. Then I came home and it wasn't quite as loud as it originally was, but it was still there. Most annoyingly, it was there in my bedroom at night.

My SO never heard it. I kept on questioning my sanity. Sometimes I could hear it in other quiet parts of town. There were times I'd go into a favorite coffee shop to work and turn right around, because the hum was strong in there. I'd generally stop hearing it if I left my neighborhood.

And every time I'd go on a trip? Nothing. No hum. Even in the middle of the night. But the fact that only I seemed to hear it kept making me wonder - is something wrong with my ears? Or do I just have a range of hearing that extends lower than most people? I got in the habit of wearing earplugs at night and using noise generators to somewhat block it out (hooray for mynoise.net) via a small iPad sitting under my pillow while I slept with the ear that heard it the most, but I still had a lot of trouble sleeping. Sometimes I'd try sleeping in one of the other rooms to get away from it a little.

And then, after about a year or two of misery because I could never get a good night's sleep, I moved to a different city entirely. It's gone. I've almost forgotten what it was like to live with that oppressive, constant, maddening noise that nobody else heard. Every now and then I'm reminded of that and I am super grateful that it's gone.

My suspicion was always that it was something to do with the subway expansion, my apartment was right above the line being dug north from the University District. Some ventilation fan that was making a noise that reverberated through the ground and came up in my ground-floor bedroom. I'll never know.

I did a lot of reading about these sorts of things during this period. Some Hums get found: The sound of a thousand air conditioner fans droning 24-7 to keep a data center cool. A misaligned pump. Fish mating calls. These are all things that a Hum has been verifiably traced to, and stopped. Some Hums never get found.

And it's fucking maddening because everyone you talk to about it is all "maybe it's just tinnitus" even though it stops when you go somewhere else.

It would be interesting to gather hum-hearers together and run some experiments. I'm also in Seattle, I also hear the hum, and like you, my hum is very location-specific.

I am no longer in Seattle but I would be totally up for this if I was!

This was in a ground-floor apartment at 50th and 11th NE in the U, if you are curious.

Forget about the stops if you go somewhere else. If you put earplugs (finger) in your ear and volume goes down then it is external.

Ear plugs don't work well with low frequencies

True. But a least a little? Or if low frequency sound is actually not transmitted through air but through the floor and body then one could step on something soft.

It helped a little. I think some nights earplugs was all I needed. I went through a lot of them.

Other nights, I needed more. And even with them it was still audible, even on a “good” night.

I'm curious; have you tried cutting out caffeine for a couple of weeks?

I was drinking a much lower dose of it than the average Seattleite, one of my favorite workspaces was a local tea shop with a lot of non- or low-caffeine drinks, I'd usually get some chai or a mug of cocoa at coffee shops.

I remember something on HN about large cooling systems for data centres being responsible for some of these hum noises, but i can't find the reference.

Could this be it?

https://www.theatlantic.com/magazine/archive/2019/11/the-end...

Yep! thats it, thanks!

My guess was cooling systems in general. I lived uphill from a residential complex and the units on the roof pointed directly at my house. The hum drove me nuts, but it was below any legal noise threshold. It was louder inside my house than outside.

Yes resonances are a fun thing. For very little vibration input, you could get exceptionally large acoustic output.

isn't it also quite possible that there simply is no external source at all and this is just some kind of disease like a tinnitus? Tinnitus is quite common with IIRC 15-20% of people having it to some degree, so the 4% of people reporting hearing the hum seems possible. Maybe it's more common in urban areas because people in urban areas suffer more from loud noise pollution.

> “Moreover, despite a number of reports, MacPherson is not convinced the Hum has ever been recorded, even by sophisticated audio equipment.”

I found this to be the most relevant part of the article. There was a side investigation into electromagnetic effects but this was disproven with a faraday cage.

So... this “mystery” seems to be plain old tinnitus, albeit a low frequency version.

By now, it should be pretty much well known that the hum is produced by the Caponians in their effort to subdue humanity: https://en.wikipedia.org/wiki/Zak_McKracken_and_the_Alien_Mi...

For many, I think the "global Hum" is too much caffeine :-)

See https://www.audible.com/pd/Caffeine-Audiobook/B083MVZ91Y

Maybe we should start worrying when the hum stops:

The Machine Stops - E.M.Forster

https://en.wikipedia.org/wiki/The_Machine_Stops

I nearly fell out of my couch laughing! I guess none of these people have ever lived on a boat. The hum is/are boats, you can hear them pretty far inland too, especially late at night!

I nearly fell out of my couch laughing!

I lived in 3 different islands with tons of boats (from cruise ships to yaughts, to tankers, to cargo), have never heard "the hum" (nor has anybody else complained or mentioned any of the thousands there), don't even know what you're on about...

Not everyone can hear it (like my wife) and if you live on the water, it's pretty obvious it's the boats. It's when you don't live near water and you hear it at 2am, and go "wow, that's really interesting," and then go to sleep.

I literally haven't thought much of it until reading this article, other than passing observations. For example, I've noticed it's not audible in every house, and usually not audible on the ground floor when it is audible on other floors.

>it's pretty obvious it's the boats

What exactly about "the boats" would it be? The motor? The propeller?

Doesn't sound like a thing...

It definitely is a thing; see my reply above. It's the engines. I was able to experimentally connect /one/ source of hum to tug boats specifically. Interestingly, though, the huge container ships that passed by did not make an audible noise.

One unfortunate effect of the name "the hum" is it kind of implies a single source. Realistically, it's probably a whole collection of sources, including some real physical phenomena, and some tinnitus-like audio hallucinations.

Not sure what it is specifically. When living on a sailboat, under the waterline, you can hear it quite distinctly.

Feel free to update the wiki https://en.wikipedia.org/wiki/The_Hum instead of squandering all that knowledge!

Ah that's a good idea. It doesn't bother me at all (since I know what it is, it's rather comforting and brings back good memories) but never considered that it might bother people who have no idea what it is (I've heard it as far as 20mi/30km away from a shipping lane in the US.) I live about 1mi/2km from a canal that regularly has barge traffic late at night. I'll see if I can find a mic or equipment that can pick up the hum, then do a little study. It'll be fun and also make it easy to reproduce around the world.

Edit: I've also considered that the frequency could be a resonant frequency in the human body for some people, making it seem unnaturally loud. My wife can't hear it.

> I've heard it as far as 20mi/30km away from a shipping lane in the US

Have you taken a look at The World Hum Map (linked from the article)? There are a lot of data points that are deep inland, way more 30 kms. For example there points in the Australian outback, and all through the "flyover states" in the US.

I did, a lot of cities are near navigable rivers that barges go down. I don't think all hums are boats, but I'd be willing to venture that most near waterways are.

I work in acoustics. Very familiar with data acquisition and processing. Hit me up if you need any processing help.

That would probably end up getting reverted because wikipedia forbids original research

For coastal city dwellers, I think it's likely that marine traffic is a major source of the hum, but the world hum map has a lot of reports from far inland that aren't explained by that.

I used to live in a place that overlooked a shipping channel. I could perfectly tell you when a tug boat was near based on the low, resonating hum of its engines. I confirmed that theory with marinetraffic.com, and it was a relief to know I wasn't hallucinating.

I have since moved, and started hearing "the hum" in March. I'm now about five miles inland from that port, but I hear the hum louder than I ever did from passing boats. I can't match it to any specific marine traffic, although the sound is nearly identical. It could be nautical, or it could be some other industrial noise, or it could be something like tinnitus.

My wife can't either either sound.

I’m curious, can you hear electronics? I can hear a CRT TV from almost 100ft away (the TV being muted, of course) and can tell you when it’s off and on without seeing it (it used to be a fun party trick back in the day). I can also hear capacitors in general if I try (but I just tune it out or I would go insane).

Those “how old is your hearing” sites peg me at 14 though I’m actually double the age and then some.

Yes, I can hear the high-pitched CRT TV noise. And also the high-pitched squeal that some CFL-backlit LCD monitors used to make. I'm not sure if it's that my ears are better, or if I'm just hyper-sensitive to sounds that other people filter out subconsciously.

Why would people in the same room match the sound of the hum to different frequencies? And why would no one be able to record the hum, even with "sophisticated audio equipment"? It seems like these two things would rule out nearby boats as the cause.

I suspect it’s likely to some resonance in the human body that not everyone will have an affinity for. Such that the frequency could be extremely low and it causes a cavity (like a sinus) to resonate and your ear picks it up. I don’t have any proof of that, but it’s a possibility.

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