Disrupt this mechanism by adding noise, and it takes us longer to make the comparison and correction. Durations tend to increase, in a manner that is fairly consistent on a per talker basis, but almost random across a talker population. Some folk produce speech in a virtually feedforward more. And, it's often an issue in any command and control application. Increase the talker's cognitive load, and less attention goes into speech production.
Durations lengthen, but variance also increases.
Again, this varies across the talker population. Not sure if this still falls into the Lombard effect bin, or is more an example of a Hanley reflex.