Yes, you can (with some quirks). Check out [Deprecated] Google Assistant Relay V2.0 - Google Home Audio Notifications!. I use this in conjunction with several Google Home devices. The two biggest issues I have are that the notification audio is not synchronized across devices (though I think there might be a semi-workaround for this if you’re welling to accept its side-effects); and that a bit ago, Google in its infinite wisdom, decided to preface each announcement with “broadcast from your user name”. So I’ve just had to get used to hearing “broadcast from Rob, laundry room door opened” every time.