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There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
141–150 of 304 posts
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#142Here's another Hum
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#143As 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…
Some googling yields this: 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 de…
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.
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#144Earlier quoted context omitted.
Are those common?
I don't have very accurate data on how many xkcd fans in Canada are trying to recreate what-if articles.
I built a laser once. Based on the crappy efficiency my conclusion would be that the chances of this happening are very low, especially in quantity, even without accurate data.
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#145We can put Hamburg (Germany) on the list of "humming cities" too. When I moved close to the harbour I started hearing a humming sound, espececially at night, almost exclusively indoors.
None of my flatmates heard that sound, so I started questioning my perception until I found another person living in the same building hearing that sound. Our bedrooms are located one below the other and the sound is most perceivable in that rooms, but we can hear that sound at other places inside the building too while others can not.
Some time later, articles in various local newspapers about that hum appeared (search for "Brummen Hamburg" if you're interested, unfortunately only articles in german), telling stories about various people along the river "Elbe" hearing that hum. I started reading about the Windsor and Bristol hum that time too.
A local politician started investigating that issue together with scientist from a technical university but - besides some theories (e.g. a big power plant) which couldn't be proven - with no success. The acousticians where cited that some of them could hear the hum at various places too, but in terms of sound level they couldn't measure it distincly from the "general" background noises of the city (with harbour, industry and much highway traffic).
In the last few years there wasn't much news about it but the hum is still there in varying intensity and duration.
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#146As 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…
Maybe it was this? 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.
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_insta...
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#147Sometimes I've wondered if this couldn't be caused by turbulence in magma or some other fluid under the Earth's surface.
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#148Earlier quoted context omitted.
How does one eliminate the noise? One of those sensory deprivation chambers? Audio insulation?
There is nothing to insulate against these large, low frequency waves. They penetrate solid rock. Perhaps enough water could absorb the waves and dissipate them, but that's not really an option.
When doing laser holography the standard practice is to build a large, heavy bed, like a sturdy wooden frame filled with dry sand, and lay that on top of something that absorbs vibrations like a series of tires and inner tubes.
That usually does a good job of sponging up any low-frequency vibrations so long as you don't have any harmonic issues.
If you were battling a persistent hum you'd have to engineer the floors in your house to be floating in this fashion, if not the entire house.
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#149As 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…
Maybe it was this? 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.
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!
Re: There's a Persistent Hum in Windsor, Ontario, and No One Knows Why
#150Earlier quoted context omitted.
Just install the debugging microphones all over, collect the data, find the source (if it's real).
Why install anything? Fly a drone around to take 5s recordings at points on a grid.
Since cities support parallel execution you must have an array to capture coherent debug information.