Why is my computer making the "delete" noise when I open it?

[oxband]

Some months ago, my MBP started making the noise made when you send something to the trash whenever I open it up from sleep. It never used to make this noise when woken up. Any thoughts? I worry it's a bug or virus of some kind.

 

[And1ss]

I think this happened to me ever once a while, my best guess is that the OS is cleaning some cache or something like that. Not too sure, but I dont think its a virus.