Many of LTS's 'Laptop Classrooms' and other facilities provide only a VGA video input and a separate 2.5 mm Audio jack to access the room's sound system. This can cause an issue when connecting newer laptops using HDMI to VGA adapters. The laptop automatically disables the standard audio output jack when the adapter is connected to the HDMI jack, and routes its audio signal to the HDMI port. To access the audio stream, your HDMI adapter must be equipped with an audio output jack. Generally, this also requires that the adapter also be connected to a source of power -- usually a USB port. The diagram below shows the connections needed for such a connection (click to enlarge).