Annoyance! lets you choose from a selection of 12 different noises, simply by clicking on the corresponding picture in the single-page user interface.
The noises you can choose from are as follows (I've put an annoyingness rating out of ten for each one): baby crying (7), fingers down a blackboard (8), car horn (4), slurping (7), chainsaw (8), hyena (3), jackhammer (8), ambulance siren (7), radio knobs being turned (8), hiccup (3), squeaky toy (9), man screaming (6).
To be honest, I'm not sure who Annoyance! is really aimed at, other than childish pranksters who want to wind people up by playing these awful noises on the bus. Personally, I would never want to inflict the sounds on anyone and I certainly don't want to listen to them ever again.
So if you do download Annoyance! then please stay out of my way.