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this post was submitted on 10 Jan 2024
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datahoarder
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It’s not an intentional noise, it’ll be a shitty bridge rectifier.
It’s just a cheap shitty power supply.
What's a bridge rectifier?
The power supply is "universal" (comes with different attachments for different regions' outlets), so I could see it doing something weird like that.
But it only happens when it's plugged into the outlet, but the HDD is NOT plugged into the computer.
Could it be expecting some extra power from the PC or something?
No, it’s nothing to worry about, it’ll be just a handful of super cheap parts in the power supply. Essentially when the power supply converts ac to dc, it has a bunch of standard parts, and if you cheap out on them, sometimes they make high pitched noises. The noises can vary in pitch too.
It's not the bridge rectifier, but it's an artifact of the operation of the switchmode power supply. Similar effects are often described as 'coil whine '.
The switching operation varies in duty cycle and frequency depending on load, and isn't absolutely stable so oscillates a little bit. This switching supply is often in the audio range; typically between about 5kHz and 200kHz depending on design and load.
Changing current and magnetic field causes the physical components (particularly transformers/inductors) to change size and shape, and this vibration causes audible noise. At some conditions, it will resonate at an audible frequency and be loud. At other conditions, it might not resonate and/or the frequency is outside the audible range, so it's silent.
Mains transformers do the same, causing the characteristic 50/60Hz hum. You'll also hear the same out of cellphone chargers.
Nothing to worry about.
Thank you for that! I've gotten into the habit of unplugging both cables (power + data) when I'm done with it, which is probably better anyways...but at least now I don't have to fret if I forget one.
(Always safely ejecting, of course!)
Thanks!