The Lenovo Yoga's have HDMI, and by default HDMI has the ability to push audio. The problem is that most podiums on campus do not use HDMI for audio and you must use the headphone jack.
When you plugin your laptop to HDMI, it will try to send the audio out this line by default. You'll need to manually tell the system to send the audio out through the audio jack. Here's how to do that.
First, connect both the HDMI cable and audio cable.
Once connected, right click on your speaker icon in the system tray near the time.
Select Playback devices from the menu
You should see at least two audio devices on the Playback tab. One of which will be Speakers/Headphones. Click on that one and then click Set Default at the bottom.
This will force the audio out the headphone jack instead of the HDMI cable.
Once done, if you reconnect your laptop to an HDMI source that does support audio, you may have to come back in to these settings and select the HDMI source as the default.