How to detect iphone is on silent mode

The reason Pirripli's code does not work is that the simulator does not support the test and the code does not check for errors. Corrected code would look like:

CFStringRef state = nil;
UInt32 propertySize = sizeof(CFStringRef);
AudioSessionInitialize(NULL, NULL, NULL, NULL);
OSStatus status = AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);

if (status == kAudioSessionNoError)
{
    return (CFStringGetLength(state) == 0);   // YES = silent
}
return NO;

For completeness, building off this link from Dan Bon, I implement the following method to solve this problem in my apps. One thing to note is that the code checks for the iPhone simulator first - executing the below code will crash the simulator. Anyone know why?

-(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, NULL);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);
    if(CFStringGetLength(state) > 0)
        return NO;
    else
        return YES;

}

Declaring this right in the view controller, you'd simply check

if ([self silenced]) {
     NSLog(@"silenced");

else {
     NSLog(@"not silenced");
}

Or, obviously, you could declare it in some kind of helper class. A more elegant solution might be a category addition on UIApplication or some such other class...