If the audio cables are plugged in and no sound or sound is coming from the projector instead of the class speakers, this means the sound output may be set to the wrong source. Since recent changes in macOS sound output may be default to other sources beside the speakers.
1. Launch "System Preferences".
On the top left, select the Apple logo and then select "System Preferences".
2. Select "Sound".
3. Select the "Output" tab.
4. Other sources maybe highlighted in blue. To correct, select the proper sound output. Depending on the output in the classroom, select "Headphones" or "HDMI" for the device sound output.
