@Bent_Wrench,

I will look into this a bit more, but for the most part - these voice notifications are controlled and managed by Google, but I am not sure why only one of your devices would cause this. I have Google Homes throughout my home, and it seems to me that changes are always being made to whether or not unavailable or offline devices will provide voice feedback.

In the meantime, my personal fix for the annoying sounds and notifications from my Google Hubs is to add two steps to the routine - 

One at the beginning to turn the voice assistant's volume down to a minimum, and then another after the routing to set the volume back to however you want.

Another potential workaround for now would be to use the SmartThings integration from TP-Link and then integrate SmartThings into Google Home. The response may change as a result of how the voice assistant interacts with the integration.

  @Bent_Wrench,

I will have to mess with mine at home, to see what specifically should be added to the routine - I think there may be a separate volume for the assistant, and a delay also may be needed. I will work with it tonight to see what i can come up with. I had done this with Google Home before moving to Home Assistant, so it has been a few years and things may have changed slightly. 

And if my home assistant routine is similar to whats needed in google, i actually needed to minimize the volume rather than mute the device.