> For many listeners, they suffer from speakers talking too slowly which causes them to tune out and become disengaged. This handicaps learning instead of enhances it.

When I was in school last year I really loved online, pre-recorded, lectures for this reason. I could put speed on 1.5x or even 2x speed. If I missed something I'd tap my left arrow to go back a few seconds or write the time stamp down and come back later. Slow speaking videos drive me crazy.