If one hears the Sound at all times — 24x7 — what is it’s significance. It is much louder during meditation but loud enough at all times that it can be heard in any situation. It grows much louder at night to the point of interfering with sleep. It is in the forehead mostly but travels to the right side & top of the head. It can be likened to a roaring jet plane or a huge burning flame yet emitting sound as well. Did Yogananda speak of this phenomenon? Thank you,
Going with how you describe it, I would say that you are hearing the sound of AUM (Om) itself, which sounds like a very loud, roaring, bursting ocean, and which is perceived at the 6th chakra or spiritual eye.
Or perhaps it is one of the "baby AUM's" which can be heard in the lower five chakras when practicing the AUM Technique.
Paramhansa Yogananda definitely does speak of what you are mentioning and also offers a special AUM Technique designed to help you hear the sounds of AUM, to commune with them, and to let them lead you into oneness with God.
The AUM Technique is a part of the path of Kriya Yoga.
My suggestion would be that you learn and practice this technique as a part of your meditations. It will help you to control it, to refine the way you are hearing it, and to know how to work with it internally, in the best possible ways.