I put sound in my project for android .When I play it on Gamewindow,sound is work!But when I build it on my android mobile,the sound is not work!Why?My mobile play other game have sound no problem!Is it have some permissions unity3d for android about sound?
Surely the problem lies in the type of file format of your audio, compression, frequency and so on. Check http://unity3d.com/support/documentation/Manual/Sound.html supported formats in the Android section Audio clip. 
try editing with Audacity, export with Lame encoding to a mp3 file and load it in unity3d. Works for me.
I just had the same problem on my nexus 9.
Just reimporting the mp3 file solved it for me. In the next build the sound on android as well.