Be careful that you are not just suppressing his warnings.

It could very well be that there's an underlying issue and the sneers and growls are simply warnings. If you do not uncover the underlying issue and are just punishing him for warning your wife, he can learn to stop warning - but that doesn't mean he still won't act aggressive.

I've heard of a lot of dogs who learned not to growl - just to bite. So be very careful that you are assessing every and any possibility of his aggressive behavior and not just suppressing his warnings.