Started a Cocos2D 2.1 template (with no physics engine) in Xcode 4.5, targeted for iOS 6 and iPad. In the CDAudioManager.m file, the following code...
AVAudioSe
Instead of using delegate use notification for handling as follows
[AVAudioSession sharedInstance];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(interruption:) name:AVAudioSessionInterruptionNotification object:nil];
- (void) interruption:(NSNotification*)notification
{
NSDictionary *interuptionDict = notification.userInfo;
NSUInteger interuptionType = (NSUInteger)[interuptionDict valueForKey:AVAudioSessionInterruptionTypeKey];
if (interuptionType == AVAudioSessionInterruptionTypeBegan)
[self beginInterruption];
else if (interuptionType == AVAudioSessionInterruptionTypeEnded)
[self endInterruption];
}