I've ridden my share of planes, trains, cars, and buses, including a 3 year stint as a university campus bus driver. One of the things you quickly grow accustomed to is the volume of white noise that permeates the air - engine and passenger noise is a constant companion... well, almost constant.
There are moments, almost imperceptibly short, when the noise just simply ceases. In my life, there have been two such moments - one on a train in Japan, and another while driving a bus. No one talking. No engine noise. No bump of tires or tracks. It feels as if time has stopped. A moment of clarity. You only notice the brief respite after the moment has passed, but now the noise has returned.
Training is like this sometimes - you hit a patch of training where everything clicks. Sometimes the period passes before you realize you've stumbled onto it, and other times you capitalize on your newfound strength and energy.