"To control the volume" means to adjust the level of sound, either making it louder or softer, for example on a television or a music player. Full definition
While judges have no financial interest in the costs side of case management, they do have a vested interest in controlling the volumes of evidence. (newlawjournal.co.uk)
There are buttons on the right side for controlling the volume and turning the screen on or off. (phonescoop.com)
Otherwise, the top and bottom buttons control volume when tapped quickly. (pcmag.com)