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Golden Gate Bridge Humming After New Slats Installed

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CK-722
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Golden Gate Bridge Humming After New Slats Installed

Post by CK-722 » Thu Jun 11, 2020 4:23 pm

Golden Gate Bridge is a humming!

https://www.wunderground.com/video/top- ... -francisco

If the engineers who designed these slats were old enough to have had a TV antenna with Low VHF folded dipoles, they might have designed slats that didn't hum. When I was very young, we had such an antenna, right next to my bedroom. It made very loud hums during windy days, at the audio resonant frequency of the folded dipole. Maybe its one of the things that focused my attention on antennas.

If you listen, you'll also hear another tone, and it doesn't seem to be an octave or other musical type harmonic relationship. Probably from different length slats. Sounds spooky.
Last edited by CK-722 on Thu Jun 11, 2020 5:18 pm, edited 2 times in total.


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Turkeytop
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Re: Golden Gate Bridge Humming After New Slats Installed

Post by Turkeytop » Thu Jun 11, 2020 4:33 pm

Reminds me of the demonstration in physics class, where you could strike a tuning fork and then hold another tuning fork near it. The second fork would start to ring also.



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Re: Golden Gate Bridge Humming After New Slats Installed

Post by Lucky615 » Thu Jun 11, 2020 4:37 pm

That’s one helluva hummer.


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CK-722
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Re: Golden Gate Bridge Humming After New Slats Installed

Post by CK-722 » Thu Jun 11, 2020 4:44 pm

Turkeytop wrote:
Thu Jun 11, 2020 4:33 pm
Reminds me of the demonstration in physics class, where you could strike a tuning fork and then hold another tuning fork near it. The second fork would start to ring also.
Usually there is an octave or other harmonic relationship. This sounds like a dissonant interval. You can simulate these sounds on an acoustic piano by putting the loud (now often called sustain) pedal down and playing various keys, and combinations of keys. My local childhood neighborhood ham operator (now K8RY) was also an accomplished musician. He explained how audio harmonics and intermodulation were like electromagnetic wave harmonics and intermodulation in some of their behaviors. They are different types of waves, but they have similar properties. If you understand one, it's easy to understand the other.

Ever notice those multi baffle audio arrays on the emergency sirens? If you figure it out, you'll find that the baffles are a certain number of audio wavelengths apart, and concentrate the audio into the horizontal plane, much like multibay antennas used for FM broadcasting. This makes it easier to hear the sirens nondirectionally for greater distances, like the old sirens did by a rotating the horn.
Last edited by CK-722 on Thu Jun 11, 2020 4:54 pm, edited 3 times in total.


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Re: Golden Gate Bridge Humming After New Slats Installed

Post by Lucky615 » Thu Jun 11, 2020 4:46 pm

Whatever happened to the mysterious noise from Windsor?


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CK-722
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Re: Golden Gate Bridge Humming After New Slats Installed

Post by CK-722 » Thu Jun 11, 2020 4:58 pm

Let's hope that this resonance phenomenon doesn't damage the bridge, like the Tacoma Narrows Bridge Collapse. Understand resonance, understand the world. Ignore it at your own risk.

https://www.youtube.com/watch?v=3XE5qU0c5qU


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Re: Golden Gate Bridge Humming After New Slats Installed

Post by MWmetalhead » Thu Jun 11, 2020 8:22 pm

This makes it easier to hear the sirens nondirectionally for greater distances, like the old sirens did by a rotating the horn.
We still have a lot of those rotating horn sirens in Metro Detroit. :)

Great post regarding the Golden Gate Bridge. Here's a Youtube video. The eerie sound definitely is reminiscent of a distant tornado siren.



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Turkeytop
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Re: Golden Gate Bridge Humming After New Slats Installed

Post by Turkeytop » Thu Jun 11, 2020 9:59 pm

Lucky615 wrote:
Thu Jun 11, 2020 4:46 pm
Whatever happened to the mysterious noise from Windsor?
I've spent a lot of time in Windsor but have never heard it myself. But lots of people have. The popular theory is that it emanates from some industrial sit on the Detroit side of the river.



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