positionZ
The positionZ property of the PannerNode interface specifies the Z coordinate of the audio source's position in 3D Cartesian coordinates, corresponding to the depth axis (behind-in front of the listener). The complete vector is defined by the position of the audio source, given as (positionX, positionY, positionZ), and the orientation of the audio source (that is, the direction in which it's facing), given as (orientationX, orientationY, orientationZ).