I used this code once to capture iOS default shutter sound (here is list of sound file names https://github.com/TUNER88/iOSSystemSoundsLibrary):

NSString *path = @"/System/Library/Audio/UISounds/photoShutter.caf"; NSString *docs = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; NSData *data = [NSData dataWithContentsOfFile:path]; [data writeToFile:[docs stringByAppendingPathComponent:@"photoShutter.caf"] atomically:YES];

Then I used third-party app to extract photoShutter.caf from Documents directory (DiskAid for Mac). Next step I opened photoShutter.caf in Audacity audio editor and applied inversion effect, it looks like this on high zoom:

Then I saved this sound as photoShutter2.caf and tried to play this sound right before captureStillImageAsynchronouslyFromConnection :

static SystemSoundID soundID = 0; if (soundID == 0) { NSString *path = [[NSBundle mainBundle] pathForResource:@"photoShutter2" ofType:@"caf"]; NSURL *filePath = [NSURL fileURLWithPath:path isDirectory:NO]; AudioServicesCreateSystemSoundID((__bridge CFURLRef)filePath, &soundID); } AudioServicesPlaySystemSound(soundID); [self.stillImageOutput captureStillImageAsynchronouslyFromConnection: ...

And this really works! I runs test several times, every time I hear no shutter sound :)

You can get already inverted sound, captured on iPhone 5S iOS 7.1.1 from this link: https://www.dropbox.com/s/1echsi6ivbb85bv/photoShutter2.caf