“3D audio” or “3D sound” refers to reproduction of natural human spatial auditory cues in loudspeaker or headphone listening situations. Stereo enhancement is to widen the stereo sound field, thereby immersing the listener in a cleaner, richer sound experience. From a practical point of view, stereo enhancement is intended to spread the stereo field into a 180 degree arc in front of the listener. The document focuses on stereo enhancement.