I've had my iPhone 4 about 3 weeks now. It's a black 16GB on Tesco, not that it makes any difference to my problem. It's just started making a new noise when locking/unlocking. Its makes the normal noise, and then for a couple of seconds afterwards it makes another electronic sounding noise. It's a different noise for locking and unlocking. It doesn't make the noise when on silent, or when lock sounds are turned off. However, it does make the noise when toggling lock sounds on and off in the settings. Any ideas? I could do a full restore etc. but i'm not really that bothered by it, it's just very odd and i'd be interested to hear ideas on why. Edit: Just discovered it makes the noise when typing with keyboard clicks on. A little more annoying. Edit2: Restarting the phone seems to have stopped it for now. Maybe it'll come back, maybe it won't, who knows?