How to reduce hard drive noise?

I would suggest you do some troubleshooting first. You need to figure out exactly where the sound is coming from.

BEFORE DOING ANYTHING ELSE create a system backup with a system image to a separate hard drive or at least to a set of DVD's.

First check your fans by just stopping them with your finger (carefully). If the sound stops there's your problem. Replace any bad fans as necessary.

Get a metal rod and place one end of it on the hard drive you think is causing the problem, put the other end in your ear and listen for excessive noise. A steady hum is probably normal but any grinding, squealing or crunching sound would indicate a problem. Note: when the heads move you will hear small clicking sounds because the heads move very rapidly-also normal. Chances are one drive will be making substantially more noise than the other. If you identify a failing drive, get a new one of the same type and replace the bad drive.

This will help you identify exactly what is causing the noise. My suspicion is that you have a bad fan.

I have owned a noisy hard drive before, and the sound I am noticing sounds very similar to that. Apparently hard drive noise is normal, but I would like to know how to get rid of it. I ran a set of HDD tests using SeaTools and my drive passed all of them, so there shouldn't be anything wrong with the drive.

This article is very old, however it's still got some good tips in it. You might want to give it a read, see if you can't make some use out of it.

I have a CM 690 II and am not overly eager about trying suspension... although I will if it's absolutely necessary. However, I would first like to see if there are any retail products that would eliminate hard drive noise (if the noise is even normal. I did not notice any noise when I first built the PC).

Hard Drive noise is not normal. One or two fans running normally should be loud enough to drown out any sounds created by your hard drive.

Its just a soft but noticeable ticking/grinding noise, not the "click of death"

You should check out Automatic Acoustic Management (AAM)
http://www.tomshardware.com/reviews/terabyte-hitachi-ac...

I used a program on my home server that allowed me to change the setting on my HDDs, the clicking noise went away and there were no noticeable affect on HDD speed.

Also in the future, you can use a cardboard tube (like from an empty paper towel roll or tp roll) to help pinpoint any weird noises.

Wait, so let me just confirm: Is the noise normal or not? It gets louder when I'm writing to the drive.

Update: I just reran a SeaTools test and noticed that ALL NOISE STOPS DURING THE TEST. Why is this so??