Not sure if this has been posted, but my Unibody trackpad is very loud when clicked and a little bit stiff too - something I noticed right away from upgrading from the "classic" MacBook Pro. I did a little bit research to see if there was a way to try an loosen the trackpad button that would also result in a much quieter click. Well, I found this article and followed the instructions:
For those wondering what screw this is, I took a photo of mine. It is the screw in the middle of the "V" on the bottom of the trackpad shell.
It is very sensitive and turning even just a fraction will have an impact on the stiffness of the click. Took me about 10 minutes of fine tuning (using a flat headed screw driver) and turning the screw even just a slight millimetre to get it perfect.
Now, my trackpad is quiet, I can actually click without getting frustrated and it does my thumb justice too!
...however, after flipping over the MacBook Pro and popping out of the battery, the user can access the underside of the trackpad where they will find one tri-blade screw. Although these types of screws typically require a special tool, this particular one is easy to turn with the edge of a small flat blade screwdriver. Turning the screw clockwise reduces the travel required to execute a trackpad click and dampens the sound emitted. Turning the screw counterclockwise increases the travel and force required and increases the noise made when the trackpad is depressed.
From experience I would advise turning the screw clockwise an eighth of a turn, testing the trackpad button and repeating until the desired trackpad button action is achieved. Turning the screw too far results in an inability to click the trackpad at all. If this happens, back off a little by turning the screw counterclockwise an eighth of a turn.
For those wondering what screw this is, I took a photo of mine. It is the screw in the middle of the "V" on the bottom of the trackpad shell.

It is very sensitive and turning even just a fraction will have an impact on the stiffness of the click. Took me about 10 minutes of fine tuning (using a flat headed screw driver) and turning the screw even just a slight millimetre to get it perfect.
Now, my trackpad is quiet, I can actually click without getting frustrated and it does my thumb justice too!