your computer presentation includes sound and you did not connect
it to the projector's DisplayPort or HDMI
port, you can still play sound through the
projector's speaker system (PowerLite Pro
. Just connect
an optional 3.5 mm stereo mini-jack audio cable as described here.
Note: If your
projector does not have an internal speaker system (PowerLite
Pro G6870/G6970WU), you can play sound by connecting
external speakers to the projector.