In case anyone else is looking for a solution....

For weeks I had been plauged by an annoying sounds of a water drops
(like a leaky faucet) most everytime a page was loading in MS Internet
Explorer. For fear that IE had been highjacked I ran various spyware
dectectors but was unable to locate the source of the sound.

Turning off sounds in IE also did not remove the problem.

SOLUTION
Eventually, I discovered that the software PestPatrol was the culprit.
By default it generates a "plop" sound anytime it blocks a cookie. To
solve this, remove the CookieCrunch.wav file from the PestPatrol
folder.