To dream of humming with your voice represents trying your best to keep spirits up all the time. Negatively, humming may reflect a last ditch effort to feel good when all else has failed.
To dream of hearing a humming sound may represent your awareness of something beginning to do something all the time.
Example: A man dreamed of humming with his voice. In waking life he was trying to calm family members down who were fighting over their deceased Grandmother’s will.