Trying to speak with no sound coming out is one of the most familiar dream experiences. It is traditionally read as feeling unheard, or holding back something important.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.