Noise tolerance is not my strong suit, which may actually be an understatement. I come by it honestly, in my family. Many a night I can recall being almost blissfully asleep, when my sister would suddenly awaken me by hissing my name or hitting me, sometimes with pillows, because the sound of my breathing was annoying her and keeping her from sleeping. (I have allergies.)
I’ve written before about my new cubicle neighbor, the one who’s on a job rotation. Well, ever since he became my neighbor, my limited noise tolerance has been pushed to the brink of breaking. Truth. For evidence I include below an excerpt of an actual instant message conversation I had with my sister:
That was in October of last year, around the time of the garbage saga, and suffice it to say, things haven’t gotten better. My workdays since then have been a long, seemingly unending loop of that scriiiiiiitch-scriiiiiitch-scriiiiiiiiitch noise that some mice’s scroll wheels make when used. It’s loud enough to be audible when I have headphones in and a decent, hearing-preserving volume set on my iPod.
But since I was told by multiple other coworkers that I really couldn’t say anything to the new guy without being unforgivably rude, I bore up in the face of this adversity and persevered. There are countless annoying habits I have, I would tell myself; I don’t like it when people use my garbage, for one, and I type with feeling. But there’s just something about that scriiiiiiiiitching noise that makes me want to run screaming through the hallways, you know?
Once I had even plotted with another coworker about secretly replacing the mouse when the new coworker was away from his desk, only to discover that he was using a model that was non-standard for our company and would clearly notice the difference.
And then today happened.
Today during lunch, my boss, who sits several cubicles away from myself and my new coworker, suddenly said, “That’s it!” and walked out to address us. To my newish coworker, he said, “I am getting you a new mouse this weekend.”
Whereupon I kind of lost it and may have said, “I’m so glad someone said something” while choking back tears of relief*.
* This is an exaggeration intended to heighten the comedic impact of this story. But I really did say that.
Ms. Grammarian 
You know, I remember our childhood so differently! :)
I have no idea how many years late I am in replying here, but there are computer mice now with a kind of touchpad surface, that scroll in any direction without the wheel (similar technology to the mousepad on a modern laptop). Apple makes a sublime such mouse, it is absolutely silent.
Of course, if your coworker was using such a peripheral, you’d just hear something else that would drive you nuts. Misophonia is a pain in the ass that way, as I’m sure you know.