I’ve had a few people now ask me about this problem. It seems to affect almost all models of iPhone and iPod. The problem is basically that while you are listening to music or an audiobook the iPhone randomly and without warning jumps into voice control.
I’m 99.99% certain that this isn’t a software problem and as far as I can tell it only happens when you are moving with the iPhone – if the iPhone or iPod is stationary on a desk or table I’ve never seen it happen.
The problem therefore seems to be to do with the electrical connection between the headphones and the iPhone. There are a couple of things to try:
1. Try a brand new pair of headphones and see if the problem stops. With wear and tear the cable can develop small cracks in the conducting circuit which as they momentarily break and reconnect are enough to trigger voice control.
2. As a last resort try cleaning the headphone socket on the iPhone. You do this at your own risk and you need to take care not to cause any damage! When I do it I get a small cotton-wool bud and gently use it to wipe the inside of the socket. Dust from your pocket and bags can build up and be enough to stop a strong electrical connection.
Good luck and I hope one of these suggestions fixes your iPhone and stops the random voice control activation.