An echo can occur in 4 scenarios.
Scenario 1: You are on screen with a guest and you hear an echo of your audio or guests audio.
This is typically caused by the speakers on one computer feeding back into the mic. Some computers are better at handling echo-cancelation than others but the best way to prevent this is to have all guests on screen wear headphones. If you still hear a faint echo after that, try lowering the volume of your headphones and it will go away.
If for some reason you're still not able to stop the echo, you can also click on the mic on your guest's video feed to mute them when they are not talking.
Scenario 2: You are watching a Crowdcast as an attendee and hear the speakers audio twice.
This is caused by having the event open in more than one browser tab or window. Check to see if happened to have opened the Crowdcast event multiple times by accident and close all other Crowdcast pages.
Scenario 3: An admin has toggled on the "Studio Sound"
Keep in mind normally we do audio processing on the sound to do things like echo cancellation, automatic gain control, and noise suppression. When Studio Sound is turned on, this processing is turned off and may cause echoing unless all participants are wearing headphones.
White means it's OFF
Green means it's ON
Scenario 4: The host or one of the others on screen has a connectivity issue
When someone has poor internet connection or an overloaded CPU, it can have an effect on their audio quality. If they suffer a drop in their audio bitrate, this can lead to an echo.