Rubber Boxes & Carved Foam: More HDD Silencing

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2. HDD Decoupled- Mounting with Carved Foam

Mounting a vibrating or noise-making device in such a way as to minimize the mechanical coupling with the computer case is a fundamental technique used for noise suppression. It is not a new idea -- it was probably known about when the very first mechanical engines were created centuries ago.

For hard drives, an authority none other than Seagate states that a drive that sounds quietest while suspended in an acoustic measuring chamber may actually sound louder when mounted in a system, while a drive that sounds quietest when in a system may not be the quietest when tested stand-alone. This is due to the role of structure-borne acoustics (See Seagate's technology paper on HDD noise for full details). This is why devices like the NoVibes drive mount and my home-brew suspension with elastic for clothing work so well to quiet hard drives that don't have much airborne noise, yet do vibrate.

Many SPCR do-it-yourselfers have rigged up elastic suspensions and report great results. But there are cases that are not friendly for rigging up an elastic suspension, due mostly to space and mechanical considerations, and elastic tends to wear over time.

In a recent project, I was faced with this very challenge. I wanted to suspend the Barracuda IV 40G HDD at the bottom front of the case to take advantage of airflow from the front intake vent. But the 3.5" drive rack extended from the floppy drive location all the way down to the floor of the case. It was permanently attached. So there was no room to suspend it in the normal horizontal position.

A recent RMA'd drive had been shipped back in a box with a ridiculous amount of egg-carton shaped foam. That gave me the idea of carving it up and using it to cradle the drive vertically at the bottom of the 3.5" drive rack.

A picture is worth a thousand words. How about three pictures?

Does it look simple? Well it is. It took 5 minutes to accomplish with a sharp utility knife and a pair of scissors. The photographs took longer! The bottom piece has a niche for the drive to sit in; the hole in the top piece holds it in place and stops it from falling over. The foam pieces are cut so they fit tightly in place. In fact, the assembly is stable enough that I put the complete PC in my car (on the floor) and drove it 10 miles without any change or shift in position noticed when I opened it up at the destination.

Does it work as a decoupled mount? Yes, but it is somewhat dependent on the softness of the foam. The type used here is not as soft as others I have used for similar things in the past. It transmits a touch more low frequency vibration into the case than an elastic suspension, in the form a low level hum that becomes audible late at night in a quiet house. However, with softer foam, it should be on par with an elastic suspension. The foam also absorbs a bit of higher frequency noise, which does not hurt.

What about heat? I expected it would heat up a bit more with the foam around the ends, so I installed a Panaflo 80mm L fan with elastomer grommets on the front intake hole directly in front of the drive. It is rigged up to run at 6V -- the noise is audible but only if you get close enough to also hear the drive (maybe a foot or less from the front of the case). The drive temperature is maintained to a safe maximum of 40C or less under all operating conditions in a room of 20-22C ambient.

Give this carved foam drive mount a try in your next project. It is simple, cheap and effective to silence a Barracuda IV almost completely.

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