The sun represents the sounds of the "real" world that is experienced by day, whereas the moon represents the subtler sounds of dreams and the subconscious.
The equilateral cross represents the four directions, or dimensionality, through which sound is perceived, since all sound is simply kinesthetic movement, or vibration, in varying degrees. The circle divided into four sections represents the labeling and separation of sounds as they are perceived and integrated into experience. A sound is automatically attributed to a source depending upon experience, and then categorized into varying levels of importance. The sound of a human's voice is one of the most easily recognized sounds, and yet it's functionality and interpretation can range more than almost any other sound. The human voice is the center point of the circle.
The Bible may be true, or it may be flawed, or it may be both, but it says: "in the beginning was the Word." This can be interpreted on a fundamental level as sound. Sound and dimensionality are inseparable.