Apple AppleVision 1710AV - Manual (Page 109)

m If you’re using the AppleVision 1710
AV Display with another display that
records sound, turn off the microphone on the other display. With both
microphones on, you may get feedback or other interference.
Selecting Mute in an application program’s window doesn’t mute sound coming from the
display.
m Some programs cannot mute sound coming from the AppleVision 1710
AV
Display. To mute the sound, select “Mute all sound” in the Sound Window
of the AppleVision Setup control panel.
111 Tips and Troubleshooting for Macintosh Users