Hearing voices or whispers with no one there is read as inner thoughts made audible. Dream tradition listens to what they say as messages from your own depths.
Has this come up in your dreams before? What was going on in your life then?
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.