As we thank God and continue to praise him that we have received, some people begin to feel something bubbling up in their belly area, like a river wants to pour out of them, they may 'hear' or 'sense' strange sounds rising up from deep within or popping into their mind. This is the Spirit giving them the utterance.
At this point, it is then up to us to cooperate and flow with the Spirit by speaking forth those sounds and syllables (yes there are those who ignore and refuse the utterance, for whatever reasons). As they do so and continue in faith, sooner or later, the rivers burst forth and out comes all the words faster than a bullet train.
When this stage is reached, you no longer have to 'hear-n-repeat' -- it is spontaneous and automatic and bypasses the brain, coming straight from the spirit.