9 ms·

As one who can hear these sounds, I can attest to how maddening it is. It's even worse when (most of) the people around you can't hear it, and they don't belie

by blunte 9y ago

As one who can hear these sounds, I can attest to how maddening it is. It's even worse when (most of) the people around you can't hear it, and they don't believe you. Earplugs only make it worse, because they filter out ambient noise that otherwise helps distract you from the incessant hum. Daytime is not as bad as night because of the natural activity sounds of a city. I have read that waves and underwater currents hitting the shore (or below the shore) can cause vibrations that will translate through the earth. That could be a cause of such sounds in some parts of the world. When I lived in the mountains of Colorado, with few people around and no industrial equipment anywhere, this hum would come and go and drive me nuts at night. I finally came to the theory that it was certain wind conditions going over the mountain ridge (across the valley), creating a pressure differential on the other side of the ridge. After the differential would reach a certain threshold, the air pattern would break up and create a pooof. This is sort of like if you are sitting in front of a campfire and the flame is going mostly on just one side of a log, but every second or so it breaks around both sides. The sound is identical, but singular. Although if it happens at a fast enough rhythm, it becomes a frequency that sounds very similar to a "hum". Of course the fire burns the wood and the conditions that make that happen change soon. I have wondered what kind of measurement equipment it would take to try to identify the source... triangulate it somehow. I really wish I knew the definitive answers to some of these hums.

phkahler 9y ago
For low frequency stuff, I would suggest using an accelerometer instead of conventional audio equipment. A small one could also be placed on a large diaphragm to allow more movement at really low frequencies. I like the physiological suggestions in the replies, but I don't see how an entire community could suffer from the same thing without a common cause.
- SlowBro 9y ago
  Maybe some environmental chemical inducing tinnitus?
rocqua 9y ago
Some googling yields this: http://earthworksaudio.com/microphones/m-series/m50/ http://earthworksaudio.com/microphones/m-series/m50/ which should be sensitive enough to pick it up. Next step would probably to get a few of these, see if you can record the hum on a few of them, and then start experimenting. The theory behind triangulation is simple. But in practice, it's probably really hard to make sure all microphones have the same sensitivity. The standard approach depends on sounds being quieter when they are far away, but if one mic is naturally quieter (deeper inside the house, or more absorbant material, or just more obstacles in the way) that no longer works. The best approach would be using a phase difference to measure. Exploiting the delay due to the speed of sound. That means you need some way to synchronize the recordings. Presuming a 20hz signal, you'd need your synchronization to be better than 0.05 seconds. This also requires the hum waveform to be easy to match. That is, you'd need to be able to tell the phase offset by matching parts of the sound. You could also try a 'big data' approach, just cataloging all reported cases and looking for patterns. That requires dealing with very noisy data though, as reported cases will be inconsistent. This is due to people not always being home, not everyone hearing it, and no verification of reports. edit: Interesing idea: use the 'bit data' approach together with wind speed and direction. The sound should be easier to hear when the wind blows it towards you. With enough data and corresponding wind data, you might have something. Does require compensating for correlation between time of day and the wind. If wind is west in the night, and less people hear things when the wind is west, that might just be because they are sleeping.
- wl 9y ago
  I wouldn't recommend the Earthworks M50 for this application. Earthworks' design approach for these microphones is to maximize time domain performance by having excessive bandwidth, minimal phase distortion, and flat frequency response. In order to achieve this, they have to use a tiny condenser element, which has relatively low sensitivity and thus relatively high noise. If you're looking to measure things near or below the limits of human hearing, I'd recommend looking at microphones designed for infrasound rather than low sensitivity microphones designed to go into the ultrasonic range. PCB and Brüel & Kjær are the big names here. Measuring infrasound is pretty difficult, unfortunately. Most audio gear has a high pass filter, which makes sense for most uses but not this. Also, pseudo-noise from air currents is often a huge source of error.
davesque 9y ago
Maybe it was this? https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street This has been cited as a possible explanation for strange noises in the mountains at various locations and also as a possible cause of the infamous Dyatlov Pass incident.
- btrettel 9y ago
  I was getting ready to post this. The empirical equation for the frequency of the oscillation is on Wikipedia, which should allow easy testing of the hypothesis that a Karman vortex street is responsible if any particular object is thought responsible. As I recall, if the Reynolds number is too high, the oscillation will become broadband, so it won't sound as described. Of course, other fluid dynamical instabilities could be responsible, so discounting a Karman vortex street doesn't eliminate fluid instabilities in general. A more general fluid dynamical instability is the Kelvin-Helmholtz instability: https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_instability https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_insta...
- blunte 9y ago
  This is great! It's all outside my area of knowledge, but basic physics led me to the idea. At least now I know a name to describe my thought. Thanks!
- JohnJamesRambo 9y ago
  Why would a humming noise make people go crazy and leave their tents naked, cause a skull fracture and two chest fractures, remove one's eyes and tongue, etc.?
  - davesque 9y ago
    Infrasound can cause weird psychological effects. Fractured bones can be caused by carelessly scrambling over uneven terrain which the campers may have done in terror. Vortex streets can also supposedly be composed of large vortices which are like tornadoes. Maybe the fractured bones could be explained by this as well. Missing eyes and tongues can be caused by wildlife. Edited to remove snark
phlakaton 9y ago
I'm confused. The attached NY Times video clip has a very audible and noticeable hum and throb – it can't be just infrasound. Is that the actual hum people are hearing/not hearing? Or is it an attempt to reproduce it, perhaps?
- davesque 9y ago
  Yeah. I also wondered about this.
- djsumdog 9y ago
  I was looking for that too; indications in the article that people actually recorded and had waves/evidence of the hum. It's impossible to tell if the noise in the video is just stock sounds or an actual recording of the event in question.
monk_e_boy 9y ago
If I open the front window and back window in my car then drive at a specific speed I get a very weird woop-woop-woop and it feels like the air is pushing me back and forth in my seat. It pulses my head. Wonder if it is something similar.
- blunte 9y ago
  Yeah, that's the same pressure differential, building and equalizing repeatedly. Same effect, and as most people agree, it's very unpleasant.
- Mountain_Skies 9y ago
  My car does this too. No previous car I've owned has had the same issue. Hopefully it isn't inherent to modern automobile aerodynamics because I'd like my next car to be one without it.
  - dsl 9y ago
    When you put one window down, crack the other window a little bit. https://blog.caranddriver.com/explained-that-weird-throbbing-when-you-open-one-car-window/ https://blog.caranddriver.com/explained-that-weird-throbbing...
Johnythree 9y ago
I was plagued by the Hum for years. At times it became astonishingly loud. But I was able (eventually) to figure it out. Short version: I made many attempts to track it down. Used low frequency Microphones, filters, amplifiers, etc, as well as PC Spectrogram programs to try and and visualise and record it. Visited many nearby industries etc to try and find it. But none of my attempts did any good. As I'm a Radio Engineer I spent ages experimenting with VLF Receivers, Spectrum Analysers, etc. One thing I noticed however was that the Hum was much worse when I was living in a quiet rural area. One night however, I noticed that I could affect the hum by doing the swallow maneuver that divers use to equalise ear pressure. I slowly came to understand that my Hum was an internally generated sound. Apparently there are various possible mechanisms: The simplest is blood flow near the ear. But also the tiny hairs in the ear canal actually have tiny muscles which cause feed-back or "regeneration" to make our ears more sensitive, and the frequency response of each hair cell much sharper. However at times, this regeneration can slip over into actual Oscillation. This ability of the ear to actually generate sounds is well documented. It can actually be loud enough for a Doctor or a partner to hear. It's called Objective tinnitus. In my case, the Hum eventually disappeared and has never returned. I suspect that it coincided with a change in blood pressure medication, but I can't be sure. Looking back, I would suggest that it may be worth trying to amplify the sounds via a set of high-quality earphones and appropriate filters, etc, using the headphones as microphones.
- 07d046 9y ago
  If I close my eyes, open my mouth and tilt my head back I can hear a hum. Is this The Hum?
  - adrianN 9y ago
    This might be a case of https://www.reddit.com/r/earrumblersassemble/ https://www.reddit.com/r/earrumblersassemble/
    - kortex 9y ago
      That got me thinking: what if the hum is a two-part process? First, infrasound/near-DC pressure fluctuation triggers the tensor tympani reflex. Then, in susceptible individuals, the tensor muscle twitches, spasms, or otherwise locks up. Alternatively, it could be a resonance mode between infrasound stimuli and tension/relaxation of the tensor tympani. Eg. Pressure pulse -> TT reflex -> neural reflex drops as sound is blocked by TT -> repeat. Total speculation, but this would explain the person-dependent experience, as well as the inefficacy of earplugs, sound dampening, etc.
rootw0rm 9y ago
I can hear these sounds too. Earplugs definitely make it worse. I grew up in a small town right next to a huge military base and aircraft flyovers were a very frequent occurrence. To me the sound sort of reminds me of a really faint helicopter or really faint jet engine in the distance, just on the edge of hearing.
phyller 9y ago
That's funny, when I moved to Colorado was the first time I started hearing it. My wife can't hear it at all but it's so loud sometimes at night it drives me crazy. It's not in my head, it's definitely coming from a certain direction. Its very low, I can barely see it on an app I put on my phone, "Spectroid". I'm pretty sure I know what it is, the coal trains moving down the front range. The tracks are like 10 miles away but the sound is so big and low that when the weather is right it propagates for miles. If I can hear it while the train is on a 20 mile stretch of track then a new train will come before the previous fades. I'd wager that distant freight trains and a gentle breeze cause this noise for a lot of people. I used to live right next to a busy highway, and that higher pitched white noise didn't bother me once. This unstoppable deep noise is incessantly annoying.
- vvdcect 9y ago
  Was this near Fort Collins by any chance? I could have sworn I was hearing something similar.
- planteen 9y ago
  There is natural infrasound in the Front Range, caused by winds somewhere in the vicinity of Long's Peak: https://journals.ametsoc.org/doi/abs/10.1175/1520-0450%281978%29017%3C1014%3AIONMRI%3E2.0.CO%3B2 https://journals.ametsoc.org/doi/abs/10.1175/1520-0450%28197...
stuntkite 9y ago
I have been working on a project to use some DIY bone conduction "headphones" to do directed noise canceling because I'm on the autistic spectrum and loud places bug the shit out of me and make it so i can't focus. Bone conduction is neat because it works inside your head and doesn't cover your ears. I think BC noise canceling is really under explored for audio related stress issues. I'm putting a mic on the back of my head to pull the room then stereo directional mics out front to actively noise cancel the room but not the person I'm looking at in a cone that I can fiddle with. Initial tests seem to work! I'm trying to improve it with a crossover for low frequency on the jaw just under my earlobes and a mid/high driver on my temple. I think even a commercial setup for bike riders and some experimentation you might be able to find some relief. I've found them to be lacking in lower frequency which is why I'm using stronger drivers and the below the ear positioning. Might be something to try playing with. It's pretty inexpensive. I'm using "Surface Transducers" from Adafruit and an STM32F4 Discovery board to process the noise canceling (has great FFT libs). All in my current setup is maybe $150 with a couple iterations under my belt.
- ultimape 9y ago
  Could you link to the low frequency drivers? There's a bunch of stuff like that on adafruit and I wanna make something similar.
  - stuntkite 9y ago
    Sure! * Large Driver - https://www.adafruit.com/product/1784 https://www.adafruit.com/product/1784 * Small Driver - https://www.adafruit.com/product/1785 https://www.adafruit.com/product/1785 There is a wide range of transducers out there, if you start digging around the units can be hard to find. Sometimes they are called Exciters. This company PUI Audio makes a bunch. https://www.digikey.com/en/product-highlight/p/pui-audio/audio-sound-exciters https://www.digikey.com/en/product-highlight/p/pui-audio/aud... The large transducers from Adafruit are such odd components. I haven't really found anything that will push that much power, but I think there are better packages for my application. They sound great with the recommended 20w amp. Here is the STM32Discovery board I am using and the FFT libs. http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-discovery-kits/32f411ediscovery.html http://www.st.com/content/st_com/en/products/evaluation-tool... https://stm32f4-discovery.net/2014/10/stm32f4-fft-example/ https://stm32f4-discovery.net/2014/10/stm32f4-fft-example/

by blunte 9y ago

phkahler 9y ago

For low frequency stuff, I would suggest using an accelerometer instead of conventional audio equipment. A small one could also be placed on a large diaphragm to allow more movement at really low frequencies. I like the physiological suggestions in the replies, but I don't see how an entire community could suffer from the same thing without a common cause.

SlowBro 9y ago
Maybe some environmental chemical inducing tinnitus?

rocqua 9y ago

Some googling yields this: http://earthworksaudio.com/microphones/m-series/m50/ http://earthworksaudio.com/microphones/m-series/m50/ which should be sensitive enough to pick it up. Next step would probably to get a few of these, see if you can record the hum on a few of them, and then start experimenting. The theory behind triangulation is simple. But in practice, it's probably really hard to make sure all microphones have the same sensitivity. The standard approach depends on sounds being quieter when they are far away, but if one mic is naturally quieter (deeper inside the house, or more absorbant material, or just more obstacles in the way) that no longer works. The best approach would be using a phase difference to measure. Exploiting the delay due to the speed of sound. That means you need some way to synchronize the recordings. Presuming a 20hz signal, you'd need your synchronization to be better than 0.05 seconds. This also requires the hum waveform to be easy to match. That is, you'd need to be able to tell the phase offset by matching parts of the sound. You could also try a 'big data' approach, just cataloging all reported cases and looking for patterns. That requires dealing with very noisy data though, as reported cases will be inconsistent. This is due to people not always being home, not everyone hearing it, and no verification of reports. edit: Interesing idea: use the 'bit data' approach together with wind speed and direction. The sound should be easier to hear when the wind blows it towards you. With enough data and corresponding wind data, you might have something. Does require compensating for correlation between time of day and the wind. If wind is west in the night, and less people hear things when the wind is west, that might just be because they are sleeping.

wl 9y ago
I wouldn't recommend the Earthworks M50 for this application. Earthworks' design approach for these microphones is to maximize time domain performance by having excessive bandwidth, minimal phase distortion, and flat frequency response. In order to achieve this, they have to use a tiny condenser element, which has relatively low sensitivity and thus relatively high noise. If you're looking to measure things near or below the limits of human hearing, I'd recommend looking at microphones designed for infrasound rather than low sensitivity microphones designed to go into the ultrasonic range. PCB and Brüel & Kjær are the big names here. Measuring infrasound is pretty difficult, unfortunately. Most audio gear has a high pass filter, which makes sense for most uses but not this. Also, pseudo-noise from air currents is often a huge source of error.

davesque 9y ago

Maybe it was this? https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street This has been cited as a possible explanation for strange noises in the mountains at various locations and also as a possible cause of the infamous Dyatlov Pass incident.

btrettel 9y ago
I was getting ready to post this. The empirical equation for the frequency of the oscillation is on Wikipedia, which should allow easy testing of the hypothesis that a Karman vortex street is responsible if any particular object is thought responsible. As I recall, if the Reynolds number is too high, the oscillation will become broadband, so it won't sound as described. Of course, other fluid dynamical instabilities could be responsible, so discounting a Karman vortex street doesn't eliminate fluid instabilities in general. A more general fluid dynamical instability is the Kelvin-Helmholtz instability: https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_instability https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_insta...
blunte 9y ago
This is great! It's all outside my area of knowledge, but basic physics led me to the idea. At least now I know a name to describe my thought. Thanks!
JohnJamesRambo 9y ago
Why would a humming noise make people go crazy and leave their tents naked, cause a skull fracture and two chest fractures, remove one's eyes and tongue, etc.?
- davesque 9y ago
  Infrasound can cause weird psychological effects. Fractured bones can be caused by carelessly scrambling over uneven terrain which the campers may have done in terror. Vortex streets can also supposedly be composed of large vortices which are like tornadoes. Maybe the fractured bones could be explained by this as well. Missing eyes and tongues can be caused by wildlife. Edited to remove snark

phlakaton 9y ago

I'm confused. The attached NY Times video clip has a very audible and noticeable hum and throb – it can't be just infrasound. Is that the actual hum people are hearing/not hearing? Or is it an attempt to reproduce it, perhaps?

davesque 9y ago
Yeah. I also wondered about this.
djsumdog 9y ago
I was looking for that too; indications in the article that people actually recorded and had waves/evidence of the hum. It's impossible to tell if the noise in the video is just stock sounds or an actual recording of the event in question.

monk_e_boy 9y ago

If I open the front window and back window in my car then drive at a specific speed I get a very weird woop-woop-woop and it feels like the air is pushing me back and forth in my seat. It pulses my head. Wonder if it is something similar.

blunte 9y ago
Yeah, that's the same pressure differential, building and equalizing repeatedly. Same effect, and as most people agree, it's very unpleasant.
Mountain_Skies 9y ago
My car does this too. No previous car I've owned has had the same issue. Hopefully it isn't inherent to modern automobile aerodynamics because I'd like my next car to be one without it.
- dsl 9y ago
  When you put one window down, crack the other window a little bit. https://blog.caranddriver.com/explained-that-weird-throbbing-when-you-open-one-car-window/ https://blog.caranddriver.com/explained-that-weird-throbbing...

Johnythree 9y ago

I was plagued by the Hum for years. At times it became astonishingly loud. But I was able (eventually) to figure it out. Short version: I made many attempts to track it down. Used low frequency Microphones, filters, amplifiers, etc, as well as PC Spectrogram programs to try and and visualise and record it. Visited many nearby industries etc to try and find it. But none of my attempts did any good. As I'm a Radio Engineer I spent ages experimenting with VLF Receivers, Spectrum Analysers, etc. One thing I noticed however was that the Hum was much worse when I was living in a quiet rural area. One night however, I noticed that I could affect the hum by doing the swallow maneuver that divers use to equalise ear pressure. I slowly came to understand that my Hum was an internally generated sound. Apparently there are various possible mechanisms: The simplest is blood flow near the ear. But also the tiny hairs in the ear canal actually have tiny muscles which cause feed-back or "regeneration" to make our ears more sensitive, and the frequency response of each hair cell much sharper. However at times, this regeneration can slip over into actual Oscillation. This ability of the ear to actually generate sounds is well documented. It can actually be loud enough for a Doctor or a partner to hear. It's called Objective tinnitus. In my case, the Hum eventually disappeared and has never returned. I suspect that it coincided with a change in blood pressure medication, but I can't be sure. Looking back, I would suggest that it may be worth trying to amplify the sounds via a set of high-quality earphones and appropriate filters, etc, using the headphones as microphones.

07d046 9y ago
If I close my eyes, open my mouth and tilt my head back I can hear a hum. Is this The Hum?
- adrianN 9y ago
  This might be a case of https://www.reddit.com/r/earrumblersassemble/ https://www.reddit.com/r/earrumblersassemble/
  - kortex 9y ago
    That got me thinking: what if the hum is a two-part process? First, infrasound/near-DC pressure fluctuation triggers the tensor tympani reflex. Then, in susceptible individuals, the tensor muscle twitches, spasms, or otherwise locks up. Alternatively, it could be a resonance mode between infrasound stimuli and tension/relaxation of the tensor tympani. Eg. Pressure pulse -> TT reflex -> neural reflex drops as sound is blocked by TT -> repeat. Total speculation, but this would explain the person-dependent experience, as well as the inefficacy of earplugs, sound dampening, etc.

rootw0rm 9y ago

I can hear these sounds too. Earplugs definitely make it worse. I grew up in a small town right next to a huge military base and aircraft flyovers were a very frequent occurrence. To me the sound sort of reminds me of a really faint helicopter or really faint jet engine in the distance, just on the edge of hearing.

phyller 9y ago

That's funny, when I moved to Colorado was the first time I started hearing it. My wife can't hear it at all but it's so loud sometimes at night it drives me crazy. It's not in my head, it's definitely coming from a certain direction. Its very low, I can barely see it on an app I put on my phone, "Spectroid". I'm pretty sure I know what it is, the coal trains moving down the front range. The tracks are like 10 miles away but the sound is so big and low that when the weather is right it propagates for miles. If I can hear it while the train is on a 20 mile stretch of track then a new train will come before the previous fades. I'd wager that distant freight trains and a gentle breeze cause this noise for a lot of people. I used to live right next to a busy highway, and that higher pitched white noise didn't bother me once. This unstoppable deep noise is incessantly annoying.

vvdcect 9y ago
Was this near Fort Collins by any chance? I could have sworn I was hearing something similar.
planteen 9y ago
There is natural infrasound in the Front Range, caused by winds somewhere in the vicinity of Long's Peak: https://journals.ametsoc.org/doi/abs/10.1175/1520-0450%281978%29017%3C1014%3AIONMRI%3E2.0.CO%3B2 https://journals.ametsoc.org/doi/abs/10.1175/1520-0450%28197...

stuntkite 9y ago

I have been working on a project to use some DIY bone conduction "headphones" to do directed noise canceling because I'm on the autistic spectrum and loud places bug the shit out of me and make it so i can't focus. Bone conduction is neat because it works inside your head and doesn't cover your ears. I think BC noise canceling is really under explored for audio related stress issues. I'm putting a mic on the back of my head to pull the room then stereo directional mics out front to actively noise cancel the room but not the person I'm looking at in a cone that I can fiddle with. Initial tests seem to work! I'm trying to improve it with a crossover for low frequency on the jaw just under my earlobes and a mid/high driver on my temple. I think even a commercial setup for bike riders and some experimentation you might be able to find some relief. I've found them to be lacking in lower frequency which is why I'm using stronger drivers and the below the ear positioning. Might be something to try playing with. It's pretty inexpensive. I'm using "Surface Transducers" from Adafruit and an STM32F4 Discovery board to process the noise canceling (has great FFT libs). All in my current setup is maybe $150 with a couple iterations under my belt.

ultimape 9y ago
Could you link to the low frequency drivers? There's a bunch of stuff like that on adafruit and I wanna make something similar.
- stuntkite 9y ago
  Sure! * Large Driver - https://www.adafruit.com/product/1784 https://www.adafruit.com/product/1784 * Small Driver - https://www.adafruit.com/product/1785 https://www.adafruit.com/product/1785 There is a wide range of transducers out there, if you start digging around the units can be hard to find. Sometimes they are called Exciters. This company PUI Audio makes a bunch. https://www.digikey.com/en/product-highlight/p/pui-audio/audio-sound-exciters https://www.digikey.com/en/product-highlight/p/pui-audio/aud... The large transducers from Adafruit are such odd components. I haven't really found anything that will push that much power, but I think there are better packages for my application. They sound great with the recommended 20w amp. Here is the STM32Discovery board I am using and the FFT libs. http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-discovery-kits/32f411ediscovery.html http://www.st.com/content/st_com/en/products/evaluation-tool... https://stm32f4-discovery.net/2014/10/stm32f4-fft-example/ https://stm32f4-discovery.net/2014/10/stm32f4-fft-example/