Hey there, ryankup!
I'd suggest you to try the drive on another computer and see if the beep will be present there as well. This is the best way to determine what is the source of this issue. Usually if a mechanical HDD is making any kind of weird noises it is an indication of an internal/physical fault. Go through the listed failure sounds here and see if yours is similar to any of them:
http://datacent.com/hard_drive_sounds.php
The sound might be because of improper placement of the drive inside the case as well.
Either way, it's advisable to back up any data from the HDD just in case, since you suspect failure. I'd also recommend using your HDD manufacturer's diagnostic tool to test the health and SMART status of the drive. I believe you should be able to find the utility on their website.
Keep us posted! Hope this was helpful!

SuperSoph_WD