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Joined 2 years ago
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Cake day: June 12th, 2023

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  • That’s how Putin claims to perceive it, but that’s also what he would claim if his actual goal was to control his neighbours by force. And don’t forget Finland and Sweden responded to the invasion of Ukraine by joining NATO. If Russia perceived NATO as a threat, then Finland joining would make them more likely to be attacked. Clearly Finland feels NATO is making them safer or they wouldn’t have joined. And since then, Russia has moved tons of their military away from NATO borders and into Ukraine.

    In other words, I trust the actions of Finland and Russia more than I trust the words of Russia.



  • I work in railway noise and vibration mitigation, and @scrion@lemmy.world has given you a great starting point. When we build rails and want to mitigate ground-borne noise and vibration (typically up to ~200 Hz), we generally mount the rails on soft pads and add extra mass to isolate the rails from the surroundings. The exact same approach will work at your computer. We don’t typically use tuned mass dampers for ground-borne vibration, so I think that will be overkill for you, but you can try if you like.

    I wanted to suggest that, in addition to the feet/foam/plywood, you can also add a big chunk of something heavy to help with isolation. Like put a heavy rock on top of the foam, and your computer on the rock. The trick is this: if k is the stiffness of your foam, and m is the mass of everything on top of the foam, then your isolating frequency is at √(2k/m). All frequencies above the isolating frequency will by mitigated (the further above, the more they’re mitigated), while all frequencies below will be amplified.

    (Quick aside if you actually want to calculate frequency with √(2k/m): check that your units for k and m are compatible, you should end up with a result in units of 1/s, which is actually radians per second, then multiply by 2π radians per cycle to convert to Hertz).

    When it comes to measuring results, since your problem is in low frequencies, you can probably use your phone’s accelerometer assuming it reads fast enough (the sample rate must be at least double the highest frequency you care about). Mount it as rigidly as you can to your computer, since if the connection is soft, the phone will be in its own isolating system. The quickest way to test your isolator would be to hit close to the base with a hammer; impacts excite a wide range of frequencies equally, so in the frequency domain you should see vibration amplitudes following a shape something like these.

    But as @scrion@lemmy.world notes below, you don’t really care about your isolator’s response, you care about what trains are doing to your computer. However, he said one thing I disagree with: it’s not the amplitude of the acceleration that you care about, it’s the amplitude of energy, and therefore velocity. This article gives a good introduction to ways you could analyze that. But now we’re getting way in to the weeds on what should be a simple project!

    One last aside: if the vibrations in your building are bad enough, you could raise it as an issue with the metro operator. The US Federal Transit Administration sets standards that are commonly followed even outside of the US (see Table 8-1 in their Noise and Vibration Manual); if your measurements show vibration exceeding those limits then they might pay me to fix it :D.




  • I’m an engineer, and I make it a point to teach young engineers that “a ton” can mean any one of three things:

    • Short ton = 2000 lb
    • Long ton = 2240 lb
    • Metric ton = 1000 kg = ~2204 lb

    And which is being used is often not spelled out, but is just known from context, and usually should be clarified. I once nearly got in trouble by thinking a measurement was in short tons when it was actually metric tons.

    So my own act of rebellion is to use “Mg” when I’m writing my personal notes.