以下代码不适用于iOS 5或更高版本

-(BOOL)silenced {
     #if TARGET_IPHONE_SIMULATOR
         // return NO in simulator. Code causes crashes for some reason.
         return NO;
     #endif

    CFStringRef state;
    UInt32 propertySize = sizeof(CFStringRef);
    AudioSessionInitialize(NULL,NULL,NULL);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute,&propertySize,&state);
    if(CFStringGetLength(state) > 0)
            return NO;
    else
            return YES;

   }