The positionX read-only property of the AudioListener interface is an AudioParam representing the x position of the listener in 3D cartesian space.
Note: The parameter is a-rate when used with a PannerNode whose PannerNode is set to equalpower, or k-rate otherwise.
An AudioParam. Its default value is 0, and it can range between positive and negative infinity.
See BaseAudioContext.createPanner() for example code.