no audio in my iphone

Blow compressed air into the headphone jack. The phone is confused as to wheather it is in headphone mode or speaker mode because there is dust in the jack.

my iphone plays music no problem with the external speakers... but no sound on the ringer or alerts. all settings are turned on... any ideas?

This solved my audio problem on my iPhone4. I blew out the headphone jack, and ext speakers work again. Thanks for the tip!