We just tested Opera on Mac and Windows with a few different people and see no issues. It might actually be using less CPU than Chrome which is impressive. I would remove any extensions you have in your browser to see if that helps. I would also check your preferences to make sure your audio device is being seen by Opera and is set the the right default Audio device. Between this two checks it normally resolves any issues.
If you continue to have issues, please contact support so we can evaluate.