I’ve seen tons of complaints on here about the Google Assistant voice being too loud. We had the opposite problem, it was too soft.
I mentioned this to my wife yesterday and she sensibly said “just tell the Assistant what you want it to do”.
We have determined that this seems to work, addressing the Sonos:
“Hey Google, make your voice volume lower”
“Hey Google, make your voice volume louder”.
On quick experimentation, the voice seems to have four or five volume level settings (it’s hard to discern this at the loudest end). You can only go up or down by one level at a time. (At the loudest level, I tried “Set your voice volume level three levels lower” and it didn’t understand.)
I don’t know if this will also work to adjust volume for alarm tones. It does seem to work for the ‘acknowledgement tone’ that we have turned on. This is all running on a Sonos Beam.
Hopefully not a fluke for us and works for others too.
[Maybe this is not technically a question - How about we count the question as “Does this work for others too?” I would have put it in as an answer on other threads asking the question, but they are all marked as “Answered” by someone from Sonos saying “We’re aware of the issue and there is no fix”.]