Changes in volume in a dream represent changes in level of attention. For example, a dream in which you hear everything very softly, as if the volume has been turned down indicates that you should be listening carefully for a signal.
Low volume in a dream may also indicate that you feel disconnected from the world, that what happens around you does not affect you very much or that you are not having much impact upon the world.
To dream that your own voice is on a low volume represents your desire to be heard. You may need to become more outspoken in order to gain success. Loud volume in a dream symbolizes overbearing or overwhelming elements in your life.