Best way to deal with low frequency hum? (MicroServer Gen8)

Enclosures and acoustic damping to help quiet them.

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Silent but deadly
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Best way to deal with low frequency hum? (MicroServer Gen8)

Post by Silent but deadly » Tue Apr 09, 2019 11:01 am

What's the best way to deal with low frequency noise?


I've have a HPE MicroSever Gen8 with 4x 8TB Seagate Ironwolf disks installed and in terms of noise, (to my ear at least) it's actually surprisingly quiet across the higher frequencies. I'd go as far as saying I wouldn't mind having it in my office during the day... if it weren't for the low frequencies that is. The disks emit a low frequency hum that goes through walls like the Kool-Aid man. It's not an issue during the day as the server is in the oposite side of the house to my office / living room but at night it's a big issue as it's much closer to my bedroom... I can hear it even when I have earplugs in.

Is there anything I can do to reduce the effect of the low frequency, HDD hum?

CA_Steve
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Re: Best way to deal with low frequency hum? (MicroServer Ge

Post by CA_Steve » Wed Apr 10, 2019 6:12 am

What kind of low freq noise? Can you press your hand against a side and make it go away or lessen? If you decouple it from whatever it's sitting on (pick it up) does it go away or lessen?

Silent but deadly
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Re: Best way to deal with low frequency hum? (MicroServer Ge

Post by Silent but deadly » Wed Apr 10, 2019 1:07 pm

I've solved the issue but I'm going to go through the motions just in case this thread can act as a helpful resource for other users in my situation.
CA_Steve wrote:What kind of low freq noise?
It's similar to when you have a fan on your desk/floor. Specifically the way in which the fan reverberates through the surface it is standing on.
CA_Steve wrote:Can you press your hand against a side and make it go away or lessen?
No. There is no perceptible change when pressing on the outer panel (which is in a single piece on the Gen8), or on the HDD sleds.
CA_Steve wrote:If you decouple it from whatever it's sitting on (pick it up) does it go away or lessen?
This is where I must hold my hands up and admit that my testing methodology was flawed (oh the shame!).

The server is on a makeshift platform, comprised of a chopping board on top of several layers of egg crates (which is all the materials I had to hand). Back when I first encountered the low frequency hum, I created this platform to try and reduce reverberation and it worked to a limited extent. I tried adding more layers of egg crate but it started getting unstable and it made no difference to the amount of reverberation so I concluded that the low frequency hum was probably airborne, which in hindsight was clearly wrong.

The big flaw in my testing was that when I picked the server up, it never really made a significant difference but obviously, I could not and never had listen to the effect picking up the server had from another room. Thanks to my brother stopping by today, I was able to address this flaw in my test (thanks for putting the idea in my head CA_Steve!). Picking up the server does make a big difference to a listener in another room. Ergo, my make shift platform is a pile of rubbish... quite literally.

I've tried putting a layer of heavy duty bubble wrap between the chopping board and the egg crates and it's made a big difference but it's really unstable.

So now I need to figure out how to create a noise isolating platform that's stable and not too expensive.

CA_Steve
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Re: Best way to deal with low frequency hum? (MicroServer Ge

Post by CA_Steve » Wed Apr 10, 2019 1:30 pm

Try a thick dense rubber pad between the server and the floor (no intermediary materials). Maybe not the 1.5" of this example, but you get the idea.

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