Use microphone and sounds muted on iPone4 only

Hi

We develop an application that records audio with microphone. Once the recorded sound, all audio sounds of the application ahve been muted.

If it would be muted during the record only, it would be ok. I just want to know how to restore the other sounds after the record interruption as quickly as possible ( Actually, there are between 10 to 20 secondes of silence ).

Thank you for your help !