1. Generally, when surfing the Internet, the wheat is turned off, so the teacher won't hear anything when watching the video.

If you listen to the class with headphones on, you may not hear it.

If you don't wear headphones, you may hear it outside (just look at the phone model).

3. I suggest that you listen carefully when you are online. Don't think about playing mobile phone and watching Aauto faster. You should study hard, and you will have greater choices in the future.