This single file, part of the Premium test suite (track 1 on the Audio CD), contains a human voice that indicates which channel the voice should be coming from — left or right. The voice switches between the channels for one minute.
This file is useful to identify the left and right channels and ensure proper connection of the speakers.
Do this test with one set of speakers at a time, if you have more than one. If your speakers have independent volume control, make sure you adjust them to an equal moderate-to-high level.
Swap the wires for the left and right channels if they are incorrectly assigned — an easy fix. There could be cases where the same signal comes out from both sides: in this case, check the mono/stereo configuration of your equipment, and make sure the channels are not wired together.