Make sure your browser is up to date and all of your permissions are set properly.
Competing Apps or Extensions
If you are running specific apps or browser extensions it may be causing issues for your call quality.
On Macs, go to System Preferences > Security & Privacy > Privacy > Location Services. You may find that there are a number of apps using location services. Turn off the ones that you don't need to be running.
To find out if you have any misbehaving apps, go to Wireless Diagnostics > Window > Logs and enable background wifi logging, hit "refresh," then run `tail /var/log/wifi.log | grep 'SCAN request'` to get a list of PIDs requesting scans
Interfering browser extensions: It is not uncommon for some third party extension to cause problems with some websites. To test this, try using your browser through an Incognito tab or Private browsing window. If all works normally then you know that an extension is causing an issue. Unfortunately there is no way to identify which one easily. A process of elimination will need to be done on each extension to fine the one causing the problem.
Here are ones we know of that have caused users issues in the past.