Sonos binding: How to trigger upon when Sonos detected the keyword?

When the Sonos detects the keyword e.g. “Alexa” the volume for whatever is playing on the Sonos is lowered so that Alexa can hear the spoken commands. That’s great but I have other sound sources (TV) that I would like to mute at the same time to improve interception. Would that be possible? I can’t find any channel for that. The State channel doesn’t seem to work for this purpose.