Yes, the single MOST important feature of the Image Streaming process is the verbalization of sensory images that occur when you close your eyes.
Verbal thinking from the word-box of our left temporal lobe represents 2 percent of the brain activity. Off-line regions of the brain that account for much of our genius potential are brought on-line and into consciousness when we speak aloud any sensory image communication that we become aware of, even marginally. Speaking reinforces the connections and causes more of the subtle functions within our body/mind (vast experiential intelligence) to be accessible.
You can speak aloud to a live listening partner, to a tape recorder, or to an imagined listener. Speaking silently to yourself will not produce the effect.