When you see someone’s lips moving. Can you actually tell what they might be saying. Some people pray with words that are seen on their lips, but there is no sound. They whisper their concerns to God. That is a proverbial closet. Others cannot read without mouthing the words they see. It is apart of their process to comprehend the subject.
When you meditate upon the Word of God. Doe you mouth the words with your lips? Many Jewish people who are devout with their faith, go to the wailing wall and recite their prayers where people can not only see they are praying, but they can hear them in some cases.
Put the Word in you heart and mind. That is where He should be anyway.