Ever since iOS 5 on my 4 and 4S (at the start of the beta for 5 as well), there have been sound bugs and still plague the phone now. Text messages would show up, with no notification sound. Just happened a few moments ago. Emails would come in and 10 seconds later, the sound. Sometimes the sound after using Siri is super loud in the operating system and then goes back to normal after a few seconds of use. Only way to fix this is a reset with power/home button. Anyone else have these issues? It's a little annoying at times but nothing I can't live with.