You can amplify a teacher's voice for the students in the classroom while live streaming with Swivl.
First of all, please setup Integrated audio for live streaming, following the instructions provided here: Integrated Audio setup
To amplify the teacher's voice:
1. Open QuickTime Player
2. Select New audio recording
3. Click on the arrow next to the record button to ensure that Swivl Input Audio Interface (Swivl Link) is selected
4. Adjust the volume
Please note, you do not need the QuickTime to record the audio. This step merely allows you to output Swivl audio through the MacBook speakers.
1. Click with the right button on the Speakers icon at the right side of the taskbar
2. Select Sound
3. Open Recording tab. Select Swivl Audio Interface and click on Properties
4. In Digital Audio Interface Properties, open the Listen tab and check mark Listen to this device
Please note, in order not to have audio feedback, a teacher should not stand too close to the laptop/PC since the audio will come through the laptop/PC speakers.