iOS simulator no sound

Hello every one

I got a big error when I develop my game.

There is no any sounds in my app when I launched in The iOS simulator, but it has sound when I bought the mac mini first month.

OS version is Yosemite 10.10.3

Xcode version is 6.3.1 (6D1002)

iOS simulator is 8.3

mac mini serial num is C07P605QG1J2.

I reinstall the os and download the new Xcode ,but the iOS simulator still not have sound.(the machine can play other sound correctly, e.g. music in itunes

)

Please help!!!!!!

Mac mini, OS X Yosemite (10.10.3), no sound in simulator