Why am I hearing echo/weird noises?

This is caused by the audio output going into the input; e.g., a microphone picking up the output from the computer speakers.

The easiest solution is for everyone in the meeting to use a pair of headphones.

Zoom is very good at audio echo cancellation, but if it occurs, the participant responsible should move their computer speakers away from their microphone or use headphones.

Sometimes it can be caused by logging into a meeting on a PC and phone at the same time.

For more details, see this article and this zoom training webinar.