If you use new version of live page witch is mobile friendly (with huuuge deskcomputer) and you mute the audio(in that event you are listening), and you close the browser and come back to slipmat.io and your audio will be muted in next event you want to hear.
If you want to get audio un-muted again, you have to go again to mobile friendly version and unmute and then close browser again and make great comeback.