When using the HDMI cable to connect a laptop to the classroom projection systems, you may need to adjust your computer settings to get the audio to play through the room speakers.
Click the Apple Menu, then System Preferences, then Sound
Click the Volume button in the lower right task bar, then click the down arrow to expand your playback device options. Look for an Extron or HDMI option, or whatever is not the built-in speakers.
On older systems you might end up with a screen like this in the sound settings- just select the HDMI option and click Apply and OK.
As always, email askIT@amherst.edu if you need help with any of the above!