What's everyone's recommendation?

There are many different solutions I've looked at online.

Some favour some type of enclosure which si then mounted to the chassis via rubber grommets.
Some go for suspending the drive by rubber bands in an open frame
Some just have a strip of rubber which is bolted to the chassis on one side and the drive on the other.

If the noise is the whine from the drive motor, isolating it may not help.  I had a Gateway PC and the OEM hard drive (a Western Digital drive) was noisy.  I replaced it with a new drive, also a Western Digital, and the new drive was quiet.  Didn't have to do any isolation.

I have Western Digital and Hitachi hard drives in my new DAW system and they are both quiet.  The hard drives in my Corsair Carbide case are mounted with plastic inserts that slide into chassis slots.

Rubber mounts will help reduce vibration related noise.
They'll do nothing if the HD itself is loud.

If you're dealing with a noisy HD, I'd just replace it with a newer/quieter unit.
Assuming you have a good case, it should be nice a quiet.

Colin - I bought a Fractal R3 case (now superseded by the R4) for noise reduction mainly so I didn't have a racket in the background while narrating videos. ;-)

That has rubber mounts for HD enclosures. TBH I was astounded by the noise reduction. Previously I'd used the highly technical method of throwing a quilt over the case.....

After putting my system in the R3 and turning on I had to double check it was working. It is silent..... and I mean silent, there's a very faint humming with my ear against the case but that's it.

That said I do have a quiet cooler and quiet case fan as well though so I'm sure the noise of the parts will make a difference but the A/B difference between the two cases with the same internals was frankly astounding.

Wish I'd have done it years ago.

As has been mentioned, if the drive itself is noisy/loud, vibration isolation mounting will not overcome that, although installing some sound deadening lining in the case or getting a more silent case might help (sound will still get out through any openings/vents in the case).

Drive enclosures might help but can cause the drives to run hotter, so then cooling becomes necessary.

Mechanical isolation can be effective, if that is the primary noise source, as mentioned. The best solution might depend upon the particular design/layout of the case.

If you have space inside your case, elastic suspension (the "rubber band" option you mentioned) works very well and can be done quite easily unless you need to drill some holes for stringing the elastic cord through. If you do use elastic suspension, put some twists in the cords and thread some screws into the bottom mounting holes in the drives to catch the cords so the drives won't slip out from between the cords when you move the case.

If you don't have the space for elastic suspension, maybe try some rubber grommets on the drive mounting screws.

The drive cages with rubber pad isolation for mounting several 3.5 drives in several 5.25 spaces as sold by Coolermaster and Lian Li also work pretty well  and also provide a front 120 fan mounting, although it might be desirable to replace the stock fan with a quieter one.

You can get much more info in the SPCR forum if you haven't already looked there:

http://www.silentpcreview.com/

Hope that helps, Lefty!

P-90s!

Rubber grommets here, nice and quiet.

Previously I'd used the highly technical method of throwing a quilt over the case.....

Hi Karl, How long were you good to go like that. 5 min? 20Min?
I mean, I'm sure it may be a testy situation. But, Sometimes you gotta do what you gotta do.....

timidi

Previously I'd used the highly technical method of throwing a quilt over the case.....

Hi Karl, How long were you good to go like that. 5 min? 20Min?
I mean, I'm sure it may be a testy situation. But, Sometimes you gotta do what you gotta do.....

I never had any issues but I did leave a venting area at the back of the case and I also have a big old cooler on the cpu. It worked okay for reducing levels but it was never what I'd call silent. I would run for several hours like that. I'd been toying with the idea of a case upgrade but being tight fisted always put it off in favour of the more makeshift quilt method.
 
The video gave me an excuse to buy the case and I was genuinely shocked at the difference it made, it was far more effective than I ever imagined it would be. The only way I can tell if my system is on now is by looking at it for the power light. It is almost completely silent unless my ear is right next to it.
 
I also have a quiet cooler fan and no fans on my graphics cards though so there are other considerations for complete silence. The Fractal case I bought also has a case speed fan control that mounts in one of the case slots, so it's possible to slow the case fan right down when needed and have it higher for general use. I mildly overclock and even with the fan up on high I have to be very close to hear it. 

Thanks guys.

I'm not sure if it's vibration or the drive itself.

Time to whip the covers off and have a look.

If you want to know if isolation from contact with the case will help without a lot of trouble, dismount the drive, dangle it temporarily from its power cable and see if it is quiet(er). The advantage of suspending the drive, rubber pads bands, grommets etc. is that it keeps certain frequencies from being transferred to the case, and acoustically amplified/radiated by the case vibration. More likely to work on lower frequency noise in most cases (no pun intended). So the clackety clack of noisy head movement may be easier to control that way than the whine of the drive motor.

If you want to see if the drive is the source of the noise you can disconnect its power and leave it in place. Of for a more elegant test, see if the drive manufacturer's utility program has an "acoustic test" that spins the drive down and up again while you listen.

Most drive full spec sheets actually include a noise level rating. For audio work, it is probably worth looking for quieter drives in the first place.

There is always a trade off between noise dampening and cooling. One possible solution.