Look for the settings first, then the volume inside, and turn the volume to the minimum, so that even if there is news, there will be no sound reminder.
Or if you don't turn off the microphone, the sound in the online classroom will always face this situation. You just need to click on the microphone in the classroom voice to turn it off. If there is still no solution, you can consult the relevant customer service staff. They will help you choose in the background and teach you specific methods and processes.