There are many automated ways to create lip sync. Some include After Effects add-ons. Others are meant to be entire animation solutions such as Adobe’s Character Animator.
Ross Plaskow adds to his After Effects cartoon character series with a look at creating lip sync to an animation, taking more of a manual approach.
Taking more of a traditional animation approach, Ross starts out by mapping the phonemes needed to a number scale for reference. There are 8 in total. He then draws out all the phonemes for each by hand.
The numbers and order of the hand drawn mouths, become important as you will be recalling them from a precomp using the tried and true approach of time remapping.
In the end triggering the custom mouth shapes with manual keyframes looks far more like professional animation, than tracked and automated movements from character animator.
Ross Plaskow has other great tutorials in his character animation series in After Effects. His simple and non technical approach to character animation is refreshing. The tutorials tend to deal with traditional animation far more than automated tools. Be sure to check out the rest on his YouTube Channel.