I had an Outlook irritation that I resolved recently. I have many irritations with Outlook, but the one I fixed was some of the sounds it makes.
Every time I viewed a new folder, it made an irritating noise. Every time I deleted an email or RSS item, it made a different irritating noise. With no program option available other than the new mail sound, I went into Control Panel | Sound | Sounds tab for some surgery. Scroll down the Program Events list until you get to the Microsoft Office section.
To quiet the folder change sound, I deleted the value in the “Sort” line. To quiet the deleted email/RSS item sound, I deleted the value in the “Delete Row” line. Now I have blissful silence. You can also choose one of the more subtle noises if you prefer.
This will apply across all Office applications, but I can live with that. I hope this can help someone else who is tired of the noise.