Isolating hard drive whine

[[F]bernZ]

Is there any method to do this other than
1) Enclosing
2) Foaming
?

My hard drive is suspended in such a way that you can't foam it nor enclose it. There's not enough space. Perhaps some pictures are in order.

My suspension in this SFF is pretty clever, IMO.

The sewing elastic gets passed through the fan's mounting holes, through the case mounting holes for the fan, loops back in by the same method, and is pulled tight. The two ends of the elastic meet at the 5 1/4'' bay and then tied in a dead knot near the 5 1/4'' bay. The hard drive sinks were pulled from a PSU and modified to fit on the HDD.



So - any ideas? I have about... 3/4'' clearance above and below the drive to do something, but nothing on the sides.

[McBanjo]

Sandwich it with 2 thick aluminium-pieces? That's about all I can think of

[[F]bernZ]

Would that not increase the whine? IIRC, high frequency sounds are easily reflected and mass damping almost has no effect on high frequency sounds. I thought foam was the preferred method for stopping high frequency sounds?

If it is.. Any ideas on how I can use foam in this case?

[jaganath]

mass damping almost has no effect on high frequency sounds.

?
I've yet to come across a noise that can't can't be damped with the brute force application of mass. This is why steel cases contain noise better than aluminium, for example.

I thought foam was the preferred method for stopping high frequency sounds?

foam works too, but it doesn't look like you have enough room there to apply the required thickness of foam.

[[F]bernZ]

I was under the assumption that the reason heavy material contains sound better is because they prevent LOW frequency sounds from vibrating the case, not that they prevent hard drive whine?

[jaganath]

Actually I think it's the other way round, dense materials attenuate high frequency sound better than low-frequency. Believe me, a good enclosure can make a big difference, I used a Molex SilentDrive for a long time, it cut out a lot of whine, and it isn't even one of the particularly good enclosures. Hard drive whine is an airborne, not a structure-borne, sound, which these things are good at defeating.

Also, steel works better because as well as being denser it is also approx. 3 times stiffer/more rigid than aluminium.

[iamweasel]

I posted my DIY solution earlier to this thread:

viewtopic.php?t=38464

You seem to be able to handle some copper sheet so if you have any clearance (around 1mm) on the sides of the drive you could maybe check it out.

IMO it's simple and works - since you already have the drive suspended so this can help reduce the airborne noise.

Then again looking at the setup the drive looks like it would be cooled very well with the fan blowing right into it so you could possibly just sandwich the drive in two pieces foam, leaving the sides as-is since the copper plates are just to help the cooling in low airflow.

[[F]bernZ]

Hmmm. I'll check your your solution later, weasel. Looks useful though to say the least..

[jhhoffma]

Actually I think it's the other way round, dense materials attenuate high frequency sound better than low-frequency. Believe me, a good enclosure can make a big difference, I used a Molex SilentDrive for a long time, it cut out a lot of whine, and it isn't even one of the particularly good enclosures. Hard drive whine is an airborne, not a structure-borne, sound, which these things are good at defeating.

Also, steel works better because as well as being denser it is also approx. 3 times stiffer/more rigid than aluminium.

That's right, any dense mass will absorb high frequency better than low frequency as the high frequency source has a shorter wavelength which can be interrupted by a mass (the mass will absorb the energy of a smaller wavelength wave due to collision of particles, and lowering the frequency as a result of the slowing of the wave). The longer wavelength waves (low frequency) simply pass right through without colliding with those particles and losing energy.

This is why submarines use VLF (very low frequency) radio to communicate with the outside world when underwater, the low frequencies can travel through large amounts of water where high frequencies can't. It's also partly why you hear the bass of a car or home theater through the walls when you won't hear the rest of the frequencies.

Of course, once the energy of the particles gets too high and the wavelength gets so small (smaller than an atom, like gamma rays) not much will stop them, aside from lots and lots and lots of matter.

[[F]bernZ]

So if I can get my hands on a lead pellet should I use that? j/k

I tried squishing some pretty dense foam [imo] above the drive.. didn't reduce the whine *too* much..